I thought it (Snake eater) was pretty phenomenal - took a bit of time to get used to the interface (quite a few things to learn how to do and to manage), but really, one of the best game experiences I've had on the PS2. I would consider picking up the new "Subsistence" version of the game if I were you - lots of bonus materials...
http://ps2.ign.com/articles/694/694781p1.html
of course, God of War, Shadow of the Colossus and RE4 are all pretty phenomenal too...I'd recommend any of those games for PS2 owners.