Yet another vote for Metroid Prime.  I got it a year ago and just recently picked it up again and it's still as amazing as the first time I played it.  I'm also amazed at how long the game is, I would have expected it to be shorter considering the breathtaking graphics and immersive sound.  I still haven't finished it but I probably will soon.  When I originally heard Metroid Prime would be a FPS style game I HATED the idea but they implemented it so perfectly that it's really amazing.  BTW, I also have Zelda and it's pretty good but I just haven't really gotten into it yet.  Given the choice I'd pick Metroid Prime, no question.