Whats your favorite game of all time?

My all time favorite game has to be a tie between Sonic the Hedgehog 3 and Knuckles and Sonic CD. I'm a huge Sonic nerd, and I think both of these games truly got the Sonic formula down. Sonic CD has the awesome time travel gimmick as well as awesome soundtrack. (Both soundtracks are good, but the Japanese one is miles better.) Sonic 3K had awesome level layouts, new gimmicks and introduced Knuckles. I have many fond memories of playing S3K as a child, but I didn't play Sonic CD until I was about 18 or 19.