The best game I have ever played changes based on the system you are asking about.
PC= “The DOOM Series” tied for 1st with “The Wolfenstein Series”
PS1, PS2, PS3 = Tony Hawk’s Pro Skater “Series” (I like the original best)
Nintendo: SuperNES through Wii = Super Mario Brother (The original) ,Super Smash Brothers Melee, and Brawl
XBox, Xbox 360 = HALO
Gameboy, Gameboy Advance, Gameboy Color = Tetris
These are the ones from Systems I owned (Or own now) and every system I listed was mine at some point.