Operation Wow has enemies pop out of a fixed environment like the old arcade shooters; there's not necessarily any "rails" because the scene doesn't change as you play but it's got a really nice multi-touch interface and is a fun throwback.
Midnight Star (almost out of soft-launch) it's probably the best on-rail shooter I've played on iOS, even beats DOOM: Resurrection or Rage by a small margin.
Star Horizon takes the top spot for space onrails for me, but both titles are fantastic. I really hated what the ARC Squadron devs did with their recent stunt though. My favorite on-rails title would have to be EPOCH.2. It isnt a traditional on-rails shooter as it provides a bit of movement with your character, but it is still on-rails, and it is fantastic.
Had a short going through some of their games on my app store, hmm... not really famous for updates, but anyways, maybe this will do it: Prohibition 1930 by Microids http://forums.toucharcade.com/showthread.php?t=203430 I re-dl to make sure it works on the latest ios 8 version - yep, it does. And just in case, i recommend to begin with easy mode.
I didn't know they pulled the paid version. That's not cool. I think there's still a lot of kinks to be worked out of the digital store model. I'm surprised Apple hasn't been a little bit more proactive about it.
Don't know if it even works anymore, but Time Crisis 2nd Strike is/was pretty awesome. Mad Bullets is really good too.
I like Arc Squadron. How 'bout a few others like Last Stand, iTerrorists, and Zombie Crisis 3d? I like those a lot!
It may have gotten pulled but House Of The Dead Overkill: The Lost Reels was really good. I tried to download it on my brother's device but couldn't find it in the App Store, but if you can get it, it's a nice way to have HotD on the go.
Rage on mobile, yes it's a quite pretty iOS on-rail shooter, Rage on console or PC is a pretty good looking 60fps sandbox-ish shooter and racer that isn't on rails.
I do too and o just redownloaded it tonight! Rage isn't an on the rails game. It's an FpS for sure as you move freely rather than moving from scene to scene. Great game tho. I'm not really that big of an FPS fan but I really enjoyed the game quite a bit!