Hard to say who it would be, but here are the games that I would put as the top in each genre in the last generation
Fighting: Soul Calibur, possibly SSBM
FPS: Half-Life 2 PC
Action: GTA3 or RE4
Adventure:eh, tough to say. Can't think of many
Racing: GT5
MMO: Obviously WOW *raises flameshield*
RPG: FFX by far, ES4 comes close, but it lacks the substance that FFX has.
This will only take a moment of your time. *steals your watch*