Vanquish
This. I was hoping I'd get an achievement for completing it, tho

Vanquish
Devil May Cry 3 had a really cool interactive credits sequence, you even get an added scene if you beat over a hundred enemies.
http://www.youtube.com/watch?v=-KsGYcSp9Lw
I love it, but it doesn't look like very much fun.
FFVI and Chrono Trigger had beautiful credits sequences, largely due to the music.
God Hand, it's not even a contest.
Zelda credits are usually pretty good with the music and slow camera pans of all the game's locales but I think I'm a little bored of it now. Still Skyward Sword was pretty great because it showed you Zelda's perspective while you were busy trying to track her down.
Portal. There is no other answer!