I take it you can place entire series, as some other posters have done.
That makes things so much easier!
These were all released on the PC, and are not ranked. The numbers are merely for convenience
1: Blood
> Only the first game. Blood II was a disappointment. I really hope monolith will revive this franchise
2: Duke Nukem (Duke 1, Duke 2, Duke 3d, and Manhattan Project)
> I love the Duke Nukem games. Hell, I even played the pre-Duke 3d platformers, and I have fond memories of them. DNF however...
3: Fallout (1,2, FNV)
> Personally, I preferred 1 to 2, but 2 was still enjoyable. FNV is probably the most replayed game on my computer.
4: Stalker
> Shadow of Chernobyl and Call of Pripyat, to be exact. Clear Sky...let's say we didn't get along.
5: Deus Ex
> Both DEHR and DE are excellent games, and I enjoyed them tremendously
6: System Shock 2
> Its SS2, what is there to say
7: Bloodrayne (1 and 2)
> I love the Bloodrayne games. I find the games to be an enjoyable action filled romp, en par with Duke 3d and the Evil Dead movies. Like Blood, I hope TRI will revive the franchise one day. Properly.
8: Doom
> The great grand daddy of shooters. They don't make them like they used to.
9: The Darkness II
> Fairly fun shooter, and the story isn't that bad either. A nice change from the usual breed of FPS in this age
10: XCOM (EU and APOC)
> I have to say, I think I enjoyed the new game and Apocalypse more than the old ones. Sure, the strategy layer in XCOM: EU is lacking, but the Tactical layer is fluid and fast paced.
Apocalypse is a blast, and is a really unique game, even by XCOM standards.
Well, crap, still ran out of space.
Ok, quick honorable mentions...*takes a deep breath*
DishonoredAlanWakeTheGroundControlSeriesDarkReignHalfLifePreEACommandAndConquer(ParticularlyRA2WhichIsTheBestGameOfTheSeriesInMyOpinion)ANDDungeonKeeper2
*Pants*