I'm only just now getting around to playing through the first Splinter Cell. I still haven't played more than a couple hours of Metal Gear Solid 2. Haven't played Pandora Tomorrow, James Bond: Everything or Nothing, Viewtiful Joe, Jedi Academy, San Andreas, Halo 2, Chronicles of Riddick, Burnout 3, NFS: Underground, Far Cry. I haven't even played the original Halo for that matter.
Time is a big part of it. I don't have nearly as much as I used to. But I agree. The number of phenomenal games over the past few years has been really astounding and impossible to keep up with.
I've got a modded Xbox with about 40 games on it and most of them I haven't even begun. At least Christmas break is coming up and I'll be able to get through one or two of them. I'm really looking forward to the next Metroid and Prince of Persia game.