Grand Theft Auto: Vice City.
I rented it, thought I beat it, but then I hear that there is an additional main storyline if you manage to make enough money by doing something, ehhh, I didn't really like it that much anyways.
I did beat it ,but it took me several years to be RE:CV:X
Medal of Honor Allied Advance
I got into the omaha beach landing part, beat it, and the rest of the game just didn't feel worth playing through.
I don't think I've beat a single Tomb Raider, ever.
Quake 4, rented it, but the bloody disc was so scratched up that it wouldn't go past the second bloody level, or..was it the first, either way.
I'm sure there has been a couple more, but I just couldn't name them right name.