This one's a shaky one for me because the game itself is downright fantastic. For 2007, it looks incredible. The gunplay is super fun and the narrative is insane! And given the sci-fi elements, it leads me to compare it to Halo. It's like Halo, but on steroids, its so chaotic. However, this version of the game is a little buggy. Every once in a while my game will exit fullscreen mode and force itself into windowed mode, which I then have to revert in the options menu. Really annoying, especially when it happens during a key moment. I had one crash during the final boss, which is weird since my rig is pretty powerful (i7-8700k and 1080ti).
Another small gripe was that even in normal mode, some enemy spawns and scenarios just seemed way too difficult and/or cheap (like pinning me on a bridge between a jeep with a mounted LMG firing at me while a helicopter hovered overhead firing its mounted machine gun at me and launching bursts of three rockets at a time, effectively one-shotting me every single time until I did a panic run and jumped off the bridge. And during the final boss, getting frozen while pelted with enemy minigun fire from three different enemies and blasted with explosives while desperately trying to scavenge for ammo and fight the boss all at once).
I know, I know, "GIT GUD" and all, which I eventually did, but sometimes the difficulty spikes felt way too sudden and steep.
Overall though, drastic difficulty spikes and weird bugs aside, it's a great game, especially for its time. Had me jumping straight into Crysis 2 immediately after so I could see where the story went.

The epitome of "fine". Shooting is decent and the powers are cool but the story is lame, combat encounters in the later half are weak, and they limit your usage of the powers too much for you to really have fun with them. I think I had more fun using the speed and cloaking to skip encounters than actually fighting. There were also plenty of annoying bits like anytime you're chased by a helicopter and didn't keep a missile launcher just in case and most of the alien fights seriously overstay their welcome. The game usually keeps a good pace though and the human fights can be enjoyable when you're not needlessly overwhelmed.