I believe The Beatles: Rock Band came the closest to being perfect. Eveything about that game was just beautifully done and the only things missing was Pro Drums, an option for Keys, and a few more Beatle songs (Hey Jude, Strawberry Fields Forever, Yesterday etc. etc.)
The original Deus Ex. The storyline, the way the game world reacted to your actions and made it feel like your actions were relevant to the world around you instead of just being a static place where stuff happened to you…