Rez is an amazing and little-known PS2 game. It's the predecessor to Child of Eden on the PS3/360. Unfortunately, the series ends there, though it did get a PS4 remaster later on. This is a very unique music-based psychedelic shooter, for lack of a better term. It doesn't really seem to fit into any established genres.
Unfortunately, it's also fairly impossible to play in the original PS2 form. It's somewhat rare as is, and even if you buy a copy, it's one of those purple-disc PS2 games that barely runs right on any of the systems. That was a really common thing in 2001, unfortunately.... but I wonder what RPG Maker 2's excuse was in 2004.
In any case, emulation of this game is surprisingly easy for a PS2 game, barely an inconvenience. This is likely because it came early in the life of the system and isn't graphically advanced as a result. Enough of this extended intro, onward with the game!