Platformer: Mario 64
Puzzle: Ico. I said what I said.
RPG: The Outer Worlds
Action: Dark Souls
Fighting: Soul Calibur 2
MMO: None. They're all garbage
FPS: Half-Life 2
Rhythm: Theatrhythm
Adventure: Zelda: LttP
Racing: Gran Turismo 4
Sports: Virtua Tennis 2
Mobile: There are no good mobile games that aren't better on other platforms.
Survival Horror: Silent Hill 3
4X: Alpha Centauri
Tactical/Strategy: Brood War
Sandbox: Just Cause 2 is the only great sandbox game
Visual Novel: Phoenix Wright 2
Stealth: Deus Ex