Half Life or Halo...for very different things.

I don't see why so many are considering Bioshock on top since only Bioshock 1 was any good and the thread title clearly says series...

Bioshock!
Definetly Bioshock! every other pick is just insane

You and Boutros have my vote and support here. Half-Life was a revolution in terms of gameplay, pacing and storytelling and implemented the grandfather of quicktime events in a non-cheesy way and did it seamlessly. The music was raw and sublime and the game was even fairly big and sported incredible AI (for the time). When Half-Life 2 rolled around, it did the exact same to the genre in many of the same areas in addition to being a stellar technical achievement (the Source engine still lives and breathes and still kicks ass, Left 4 Dead 2 looks amazing on my rig) and the title that shot Steam into the masses for real and started the most brilliant digital distribution venture to date.

Holy hell, I just realized just how poor those other franchises are in comparison.

I would like to add that Call of Duty 1 and 2 had fantastic single player campaigns but the rest of the series drag the overall grade for the franchise down by miles (Modern Warfare was good though).

They're not.  Half Life franchise in general and Half Life 2 in particular remains the gold standard for FPS SP campaigns I'd say - as much as such a thing can be claimed anyway.   Halo CE had a decent campaign too although they borked the Library and some of the later levels : but Bungie were under the cosh to get the game out whatever so it's at least defensible.

I'd put System Shock 2 over Bioshock for SP and probably Deus Ex too if we're bringing in the hybrid FPS with RGP elements.  As the title says franchise I'd say that easily puts System Shock ahead as a franchise.  Deux Ex 2 and Bioshock 2 were both weaker installments.

Have you played Bioshock?

Yep. Played all the games on that list and then some, I've tried pretty much every big FPS game in the last fifteen years. I could write a long post on why Bioshock is not what it was touted to be, in fact; I've done it on many occassions.

That said, I am looking forward to Bioshcok: Infinite, if only because it looks absolutely bonkers!

Was BioShock 2 really that much inferior to its predecessor?

I think I'll have to go with Half-Life. I'm sure I've missed some other great games I would like more because I don't really think Half-Life is all that good... But it's definitely miles ahead of the games in the list up above.

Half-Life > Halo > BioShock

Havent played Bioshock so can't say anything. Although i do have part 2 just sitting there lol and im also waiting on Infinite to release since they said that the original was suppose to be on the disc. (PS3 version) From the choices there I'd choose Resistance and Killzone and i also liked the campaigns for CoD and CoD 2.