Considering how much the original Resident Evil 4 did for the franchise, it's ludicrous that the Mobile Edition even made it onto the iPhone, as it manages to undo all of RE4's innovation, reducing a great game to what looks and feels like the very first Resident Evil. The animation is terrible, the controls awkward and unwieldy, and the plot and dialogue stilted and worthless. It looks like a PlayStation One game, and that's nearly unforgivable these days, given how sharp so many other iPhone games look. Give this one a pass and go play the real thing.
This plays more like House of the Dead than any kind of Doom game. Doom Resurrection is an on-rails shooter that uses the accelerometer to aim, dodge, and shake off enemies when they grab the character. While all the usual tropes are here -- the fleshy, grotesque enemies; the washed-out monochromatic palette; the repetitive growls and wails -- the gameplay is so basic it's nearly insulting. There is almost no sophistication to this game; it's a wonder that id even released it with their name on it at all. Having said all that, if you're looking to pass some time, this will work between bus rides.
The Call of Duty series is beloved among players of World War II first-person shooters, but if all you knew of the franchise was this Zombies offshoot, you'd be hard-pressed to understand why. I'll say it directly: if your game controls require the player to obscure the action with their fingers, you've failed. This game is the hunt-and-peck method of zombie eradication, and it fails to entice. However, I understand that there is a competitive mode, so you might want to try it out if you're looking to play against others.
This time-spanning series has acquitted itself well on consoles and the PC, but its free-roaming movement seems hampered by the confines of the iPhone. Assassin's Creed 2: Discovery has been likened in some ways to playing a Sonic the Hedgehog game, in that there is a definite on-rails feel to the action, and a sense of speed that is baffling, given that its predecessors don't feature it as a selling point. Moreover, the player's fingers are all over the screen, getting in the way of the action and intruding on the ambiance of what's meant to represent the Renaissance Era of Europe. The one thing that remains, however, is the solid visceral feel of stabbing guys, so if you're craving more of that, you'll enjoy Discovery.