This game is basically everything it's cracked up to be. The levels are put together with care, the enemies are well-placed and fun to engage with, and the challenge is overall extremely satisfying. Areas are fun to explore, and the feeling when you unlock a shortcut is amazing. Each new boss you fight seems like an impossible challenge at first, until you slowly learn their moves and patterns, and by the time you've beaten them you feel like you've mastered that fight. The satisfaction you get from clearing a challenge in Dark Souls is unmatched by nearly anything outside of the series.
Unfortunately though, I've just lied. What I've described is how the game is for most of the playthrough, when it's at its best. However, Dark Souls is a game of highs and lows. For almost every perfectly satisfying moment in this game, there is one that might make you stop playing out of frustration. Notably, the quality of the level design falls off significantly in the second half of the game, with one major area in particular feeling particularly unfinished due to the noticeable lack of care put into it compared to the rest of the game.
Even after the latter-half fall-off in quality, the game is still fun, and has a few great moments in store. The DLC in particular, which is included for free in the remaster, is a shining example of what the second half could have been. The level design is of the high level of quality you would expect from the game's first half, including hidden items and fun shortcuts. The DLC bosses are just the right level of difficulty for a late-game character, creating a challenge that will keep you coming back until you've bested them.
Overall, Dark Souls is a masterclass in game design that I would recommend to anyone who is interested in the genre. It offers a more methodical, unforgiving challenge than newer From games like Dark Souls 3 and Elden Ring. Because of this, it won’t appeal to everyone, and those who enjoy From’s newer titles might have trouble with this one. Still, it’s a great game and a must-play for anyone who enjoys the genre.

This is probably the best platformer I've ever played. The controls are snappy and responsive, the levels are tightly designed, and the difficulty curve is nearly perfect. Every level is fun on the first playthrough, and still fun on a speedrun or completionist playthrough. The bonus levels explore the game's mechanics in ways you would hardly imagine when first playing the base game, while also creating some of the most satisfying challenges in any game I've played. The story is simple but does a good job conveying its themes, and the simple but well-developed characters are fun to see interact as they progress through their own arcs.