Game I like the most from that year is Fable: Lost Chapters - but that is just enhanced version of the original Fable from the year before, so can't even consider it.
I remember F.E.A.R, horror FPS - it had really good enemy AI, and with ability to trigger slow motion it felt quite different to other FPS games of that period.
Of course, Psychonauts, RE4, Shadow of Colossus, Battlefield 2 (probably most time spent in that one that year), some great adventure games like Fahrenheit: Indigo Prophecy and Still Life. And then LEGO: Star Wars. I didn't play that one until quite a few years later, but that is the one that started it all, and they were always fun to play, single or coop.
But, no matter what I think personally of playing guitar on a plastic controller, yeah, I just have to give it to Other - Guitar Hero.