Super Mario Galaxy. Innovation, content, graphics, music, controls and gameplay. Video game immersion and escapism at its best.
Xenoblade Chronicles would be my runner-up, one of the greatest RPG's ever made. Mass Effect 1&2 would be in the mix as well. Call of Duty, NSMB, Brain Age and Wii Sports should also be in the discussion for the impact they had on gaming as a whole.