Old games
Creatures 2
One of the first games I really remember digging into. I can't really tell if this game was truly deep or just fakedeep, but for me at 9 years old being able to mess around with genetics and artificial intelligence was very exciting. I remember feeling so sad when my creatures got sick and trying to heal them, but also creating horrible genetic mutants by fusing different species together. This game might be worth revisiting now that I could potentially understand what's going on.
This is also one of the first games I remember modding. There were all sorts of weird online communities where people created Christmas and holiday items that I had to install. It was all really buggy. Super super weird game and a treasure, I can't think of any other game that's been as ambitious regarding the literal genetics and hormones of artificial life. Apparently the game still has a somewhat active community that has made edits to the genome of the creatures to create more human-like behavior.
Nox
Nox was the game that gave me my passion for action RPGs. For years I thought that this game was a Diablo 2 clone but since it came out in January of 2000, it actually preceded D2 by almost 6 months. You could play as a warrior (melee), wizard (magic user), or conjurer (hybrid + summoner). Unlike other action RPGs, Nox was unique in that spells and abilities had to be aimed, adding a layer of skill to the game that a lot of other RPGs don't have. Online play had a capture the flag mode which was also unique for a RPG.
Nox was also one of the first casualties of EA. Westwood lost rights and EA took over development, where they ceased support and closed the multiplayer servers forever.
The Neverhood
The Neverhood was a point-and-click adventure game with an extremely cozy claymation art style. The whole thing feels cinematic and puts me in a weird headspace. It's a lot like Myst in that you're given no backstory and have to learn the story as you go along, but doesn't take itself nearly as seriously. The team that made this previously worked on Earthworm Jim.
Grim Fandango
Grim Fandango was another ambitious adventure game - this time in 3D. LucasArts produced this game (Monkey Island, Day of the Tentacle) so the story is top-notch. It's been remastered so a lot of the idiosyncrasies of 90s gameplay have been ironed out.
Boppin'
Very stylish puzzle game similar to Bust-a-move. Created by Jennifer Diane Reitz of Happy Puppy (now defunct gaming site, but was the place to go in the 90s-2ks). Definitely check out some gameplay on YouTube.
Operation Inner Space
Shmup that takes place INSIDE YOUR COMPUTER. This game actually used your filesystem as levels. Folders would be "infected" and you had to eliminate the virus. Great AI and tons of ships to choose from, each with their own special abilities. Cool faction system too.
Commander Keen
Commander Keen... if you don't know you're missing out. Side scrolling platformer with creative enemies and stages developed by iD software (DOOM! WOLFENSTEIN!)
Kingdom of Loathing
One of the first browser MMO's I really enjoyed playing. So much tongue in cheek humor and grindage. Glad it's still online.
Survival Project
Korean MMO arena battler. The game wasn't amazing but I learned a lot about hacking from forums and IRC channels surrounding this game.
New Games
Dungeon crawl stone soup
Classic roguelike feel with modern controls and features, and it's actively developed.