Halo 2 (PC) (2007) (Bungie) [Legendary difficulty]
8Halo 2 was the first shooter I played on a console (my then newly purchased original Xbox), but I honestly don't remember much of the game and I never played the slightly enhanced PC port until now. The most noteworthy aspect of Halo 2 on the PC is probably that it's a "Vista exclusive" and comes with Games for Windows Live integration, Achievements (even though the original version on Xbox 1 obviously didn't have any Points at all) as well as a supremely pointless but nonetheless rather impressive "start playing the game while you're still installing it" feature.
This slightly weird Halo 2 re-release didn't seem to have impressed anyone back in 2007, and it's easy to see why a 3 year old console game might not have made PC shooter fans particularly enthusiastic at the time of its release. However, compared with the first game (which I replayed in its entirety immediately before installing Halo 2) it's hard not to appreciate the sequel's vastly improved graphics, more detailed levels and increased emphasis on precision-based shooting. Bungie were working with the exact same hardware specifications (i.e. the original Xbox) but it's clear that they went back to the drawing board and recreated what worked about the first game in a new and much better engine. Also, the 3D effect while playing with NVIDIA 3D Vision is surprisingly good (despite a few technical issues) and really adds to the experience.