I voted Nazis, but only because I played way too much of the Rise of the Triad and wolfenstein 3D demos as a kid. When I think about my career as an FPS player, I managed to miss the WWII shooter boom almost completely, since at the time it was still possible to get arcade shooters, and the only game I have with a modern war them is Battlefield 2, which has the Chinese instead of the Russians, and has an actual coalition of Middle Eastern governments, instead of irregular terrorists. I played a lot of Doom as a kid, but that was demons, not aliens. I wrote all of that and then remembered that Dark Forces and Jedi Knight were both FPSs, and they both involved the occasional alien to break up the monotony of shooting Storm troopers. It's too late to change my vote, but I probably killed more aliens with two full version games than I did Nazis with a pair of demos. However, I think the mot common enemies I've fought overall have been generic futuristic soldiers, from completely made up factions. F.E.A.R. was that way, as were Shogo and, to a large extent, the Half Life games. Half Life 2 had more human enemies than alien enemies, at any rate. There's also the fact that I've logged many more hours into online fragging than offline campaigns, skewing the numbers more to variations on the player character than to any actual faction.