It seems like Star Warfare: Black Dawn is being acclaimed by a lot of people. I didn't try it yet, though.
This is pretty good, has some janky moments but is really what the ios borderlands game should have been.
Star Warfare Black Dawn Call of Duty Black Ops Zombies Into the Dead (more runner than shooter, but you might like it... it's one of the most atmospheric games on iOS and it's free.)
Alright! Dead Trigger 2 is coming soon too, that will probably rock. http://forums.toucharcade.com/showthread.php?t=173314 Dead trigger 2 thread
Fail...both of those are TPS's Try the FPS's by General Arcade to scratch your classic FPS itch. They're really good.
It depends on what you're looking for in a FPS. If you want multiplayer action, check out Archetype. If you're looking for classics, Doom, Marathon and Wolfenstein 3D. Problem is that there is only a limited number of FPS' on iOS. I don't mind the Modern Combat series but wish someone developed a good steampunk fps or a fantasy FPS like Heretic.
First off, he's asking for good iOS FPS's. Most of the ones you mentioned are not on iOS. Secondly, no one plays Archetype anymore. The game is dead.
How about Mission Europa Collectors Edition ? If you like loot / sc-fi / single person awesome indie dev / many many hours of gameplay ...