A few that come to mind for me are
- ASCII Sector - space roguelike that was released in the last 2000s
- Sonic Robo Blast 2 - free 3d sonic fangame, built using a Doom engine of all things…
- ClassiCube - free sandbox block-placing game that is similar to 2009/2010 Minecraft Classic
- Chronicles of Denzar - free browser-based RPG similar to dragon quest (previously PhantasyRPG.com) running since the early 2000’s
Big ups for Classicube, it really captures the feeling of old Minecraft way better than the classic.minecraft.net instance.
My entry would be Lego SuperSonic RC, and old shockwave 3D game on the Lego store that let you drive an Ed car around the air ducts and ramp off shelves to get points for doing cool stunts. It’s not that deep of a game but my brothers and I got a lot of mileage out of it, especially since it was one of the few games that ran on our old Windows 98 pc lol.