Neverwinter Nights 2 is a complicated animal compared to the original Neverwinter Nights game. At its core, it's the same game restomodded, but it carries with it some issues that hold it back from being better than the original.
Gameplay
NWN2 borrows a lot of gameplay elements from KOTOR where you can assume control of your companions and some conversations are letterboxed cutscenes. Inventory management is also similar to KOTOR, where the items no longer take up inventory space with unique sizes on a grid, and now all occupy one space in your inventory screen. The huge side effect to this inventory management is that you will have more trouble than necessary finding certain items that you'll need as a lot of the icons look identical.
Gone from the game is the radial system where you right click on an element and you're given a UI wheel to assign an action to your PC. In its place is a drop down menu that does the same, but removes some of the inputs to keep the menu from being cluttered. The designers ideally want you to use the hotbar more than the drop down menu, as they believed that right clicking on the enemy you want you to perform the action on, and then click on the ability in the hotbar to do that action on the enemy would be more intuitive than the radial menu from NWN.
However the hotbar is incredibly tedious to set up now that the radial menu is gone, and any special feats you want to perform must be dragged through from your characters' character sheet. I also haven't found a way to assign companion commands to the hotbar - which you could do in NWN - and those commands are an absolute necessity if you don't want your companions to aggro any enemies you don't want in a fight. The AI wants to engage in all enemies, even ones that will break your party formation.
Overall, gameplay is a downgrade from the original game.
Graphics and Sound
NWN2's engine essentially splashes the original NWN with a brand new coat of paint that looks good as screenshots but awful when in motion. All of the characters' animations feel extremely floaty, especially when attacking and moving. Not to mention that the women in the game walk as if they're always on a catwalk strutting. The spell's visual effects have taken a downgrade as well, and I was kind of disappointed with how it handled the electricity visuals on weapons. Blood also no longer spills on the ground and just floats in air like a plume of smoke.
The game has some new sound effects and music, but it also has pretty much all of the sound assets from the original NWN, and the game relies heavily on the older sounds. Voice acting in the game is a mixed bag. Thankfully, all of the companions have good VA and they don't suffer from the crushed dynamics some of the voices from Hordes of the Underdark had. Unfortunately, a bit of the NPCs aren't as lucky. Most of the bad VA come from monstrous NPCs who would benefit from having some reverb or other post processing, but they often suffer from crushed dynamics making them fatiguing to hear. The ones that speak very slow are often the ones that have the worst voice direction, but I don't think it's the fault of the VO artist.
Some of the NPCs in the NWN2 campaign even have the Asmir Male voice set, which if you've ever used the NWN Toolset, you'll know that is the default voice set assigned to any newly created NPC. It just so happens that the designers forgot to reassign another voice that would have made more sense to the NPC. There are a couple of other design oversights in the game that could take forever to fill this box of text up, but I digress.
Story
This is without a doubt the only thing that makes NWN2 better than NWN1 in spite of its problems. Pretty much all of the original Bioware modules in NWN had subpar stories save for Hordes of the Underdark. However, NWN2's story kept me engaged all throughout its long campaign, so much so that I even sat through a no word of lie a half hour conversation during a trial in the second act. Companions all have engaging side quests, and they feel very fleshed out as characters in the story whereas in the original campaign they're mostly used tools as a means to make the game more smoother to play. It's a testament of good writing if I'm able to stomach the bad animations and questionable game design choices just to see what happens next in the game.
Replayability
There are several paths you can take in the campaign and they all fit pretty well with the game's plot, surprisingly even the evil ones. Replayability in the first campaign will not be an issue if you're used to the gameplay jank. Unfortunately, because the only thing that carries the game is the campaign, NWN2 doesn't have the longevity of its older brother. Despite having its own toolset like NWN, it was reported that the toolset is more complicated to use compared to the original one, so users ended up going back to the old game for content creation. I cannot speak about the toolset as I have no recollection of ever using it, but by no means does that mean the game is void of user made content. Far from it, it has a sizeable amount of content that will garner more hours of your time if you let it, but it is nowhere near the sheer size of NWN1's content.
Final Thoughts
To put this long-winded rambling of a review short, Neverwinter Nights 2 is a great game mostly for its main campaign. Once you get used to its jankiness, the story of the campaign is among the best in the Dungeons and Dragons lore with compelling characters and decisions that may or may not bite you back in the end. If you're looking for an older RPG that feels okay to play despite its jankiness, you might want to just play NWN1 instead, as it already has loads of fan content that sometimes outshine its main campaign.
Gameplay
NWN2 borrows a lot of gameplay elements from KOTOR where you can assume control of your companions and some conversations are letterboxed cutscenes. Inventory management is also similar to KOTOR, where the items no longer take up inventory space with unique sizes on a grid, and now all occupy one space in your inventory screen. The huge side effect to this inventory management is that you will have more trouble than necessary finding certain items that you'll need as a lot of the icons look identical.
Gone from the game is the radial system where you right click on an element and you're given a UI wheel to assign an action to your PC. In its place is a drop down menu that does the same, but removes some of the inputs to keep the menu from being cluttered. The designers ideally want you to use the hotbar more than the drop down menu, as they believed that right clicking on the enemy you want you to perform the action on, and then click on the ability in the hotbar to do that action on the enemy would be more intuitive than the radial menu from NWN.
However the hotbar is incredibly tedious to set up now that the radial menu is gone, and any special feats you want to perform must be dragged through from your characters' character sheet. I also haven't found a way to assign companion commands to the hotbar - which you could do in NWN - and those commands are an absolute necessity if you don't want your companions to aggro any enemies you don't want in a fight. The AI wants to engage in all enemies, even ones that will break your party formation.
Overall, gameplay is a downgrade from the original game.
Graphics and Sound
NWN2's engine essentially splashes the original NWN with a brand new coat of paint that looks good as screenshots but awful when in motion. All of the characters' animations feel extremely floaty, especially when attacking and moving. Not to mention that the women in the game walk as if they're always on a catwalk strutting. The spell's visual effects have taken a downgrade as well, and I was kind of disappointed with how it handled the electricity visuals on weapons. Blood also no longer spills on the ground and just floats in air like a plume of smoke.
The game has some new sound effects and music, but it also has pretty much all of the sound assets from the original NWN, and the game relies heavily on the older sounds. Voice acting in the game is a mixed bag. Thankfully, all of the companions have good VA and they don't suffer from the crushed dynamics some of the voices from Hordes of the Underdark had. Unfortunately, a bit of the NPCs aren't as lucky. Most of the bad VA come from monstrous NPCs who would benefit from having some reverb or other post processing, but they often suffer from crushed dynamics making them fatiguing to hear. The ones that speak very slow are often the ones that have the worst voice direction, but I don't think it's the fault of the VO artist.
Some of the NPCs in the NWN2 campaign even have the Asmir Male voice set, which if you've ever used the NWN Toolset, you'll know that is the default voice set assigned to any newly created NPC. It just so happens that the designers forgot to reassign another voice that would have made more sense to the NPC. There are a couple of other design oversights in the game that could take forever to fill this box of text up, but I digress.
Story
This is without a doubt the only thing that makes NWN2 better than NWN1 in spite of its problems. Pretty much all of the original Bioware modules in NWN had subpar stories save for Hordes of the Underdark. However, NWN2's story kept me engaged all throughout its long campaign, so much so that I even sat through a no word of lie a half hour conversation during a trial in the second act. Companions all have engaging side quests, and they feel very fleshed out as characters in the story whereas in the original campaign they're mostly used tools as a means to make the game more smoother to play. It's a testament of good writing if I'm able to stomach the bad animations and questionable game design choices just to see what happens next in the game.
Replayability
There are several paths you can take in the campaign and they all fit pretty well with the game's plot, surprisingly even the evil ones. Replayability in the first campaign will not be an issue if you're used to the gameplay jank. Unfortunately, because the only thing that carries the game is the campaign, NWN2 doesn't have the longevity of its older brother. Despite having its own toolset like NWN, it was reported that the toolset is more complicated to use compared to the original one, so users ended up going back to the old game for content creation. I cannot speak about the toolset as I have no recollection of ever using it, but by no means does that mean the game is void of user made content. Far from it, it has a sizeable amount of content that will garner more hours of your time if you let it, but it is nowhere near the sheer size of NWN1's content.
Final Thoughts
To put this long-winded rambling of a review short, Neverwinter Nights 2 is a great game mostly for its main campaign. Once you get used to its jankiness, the story of the campaign is among the best in the Dungeons and Dragons lore with compelling characters and decisions that may or may not bite you back in the end. If you're looking for an older RPG that feels okay to play despite its jankiness, you might want to just play NWN1 instead, as it already has loads of fan content that sometimes outshine its main campaign.