Granted it cannot compete with console giants like Left 4 Dead and the Resident Evil series but I'm constantly amazed and delighted to see new Zombie games appearing in the App store! Sure there are some pretty bad ones but for every bad one there are at least 3-4 great ones! For Zombie connoisseurs I would recommend the following games from the App store:

1.) Zombie Attack! - this was one of the first Zombie games in the App store and falls into the Tower Defense genre with a twist in that you actually control a character and are not limited to a specific path that the attackers follow.

2.) Zombieville USA - This is a straightforward side-scroller Zombie shooter with great cell-shaded/cut-out graphics. The character animations and weapons are excellent!

3.)iZombie Death March - This game is a short episodic top-down shooter that provides nice variation in each level making you feel like you are progressing through and escaping a Zombie outbreak. It is short but the presentation is excellent and is a great addition to the Zombie genre.

4.) Zombiegame - this is a simple 1st person survival game in which you are assaulted by endless waves of Zombies. You are rooted to one spot and can only move your view from side to side and must frantically watch all sides to prevent a Zombie from blindsiding you. It has great watercolor/ink art and dark atmosphere. Another simple but fun game.

5.) Attack from the Dead, or AFD - In this game you must defend a single building from a Zombie onslaught by night and explore buildings for supplies and survivors during the day. The gameplay is simple as you move your character up and down behind a barricade of furniture and shoot the Zombies entering through the door. The daytime exploration is limited to tapping on buildings on a map and could have been better but add a nice touch to the game.

6.) Alive 4-Ever - This is a new game and is one of the best. This is a top-down survival shooter with some variation added to certain levels like rescuing survivors and obtaining vaccines, etc. This game has a level-up system and allows customization of one of the 4 characters (who each have their own unique attributes) through increasing attributes, purchasing new weapons, and unlocking bonus items. It supports multi player and would be a blast to play with others!

7.) Resident Evil 4 & Degeneration - Capcom brought the Resident Evil series to the iPhone in not only one but TWO games! One is a watered down version of RE4 and the other is an original title that goes along with the recent CGI movie RE Degeneration. Both play exactly the same and are decent games utelizing a "virtual analog stick" on the touch screen. This type of game is a little hard to do well on a touch-screen only platform but both are excellent games given the inherent limitations of the iPhone.

...more to come.

Here is a list of games I consider to be system sellers and are therefore among my favorites. I will begin with last generation systems and continue on to systems for which games are still being actively developed. All of these systems include many other games worthy of attention but I would not exactly consider to be system sellers. I am only including games exclusive to each system:

Nintendo Game Cube:

-The Legend of Zelda: The Wind Waker

-The Legend of Zelda: Twilight Princess

-Resident Evil 4 (this is an exception to the system specific rule as it was released on GC so long before PS2 and is the superior version.)

Playstation 2:

-ICO

-Shadow of the Colossus

-Okami (another soon to be exception to the exclusivity rule but I don't consider the Wii to be a proper gaming system for games that were not specifically designed for it's "unique" controls. If you can't tell, I'm still bitter over the GC Twilight Princess delay because of the friggin Wii version.)

-Odin Sphere (this game proves that sprites aren't dead and just how beautiful a 2D game can be on current systems. We need a revival of sprite-based 2D games like this.)

-Devil may cry 1, 2, 3 Special Edition

-MGS3: Subsistance

-Ace Combat 4, 5

-Final Fantasy X, XII (For FF fans only, though this goes without saying. I felt I had to at least include FFX as it was the first PS2 game I ever owned.)

XBOX:

-Crimson Skies: High Road to Revenge

-Psychonauts

-Thief: Deadly Shadows

-Otogi 1, 2

-Halo 1, 2

-Ninja Gaiden (Black)

Game Boy Advance:

-Advance Wars 1, 2

-Fire Emblem (Both games)

-Super Robot Taisen: Original Generation 1, 2

-The Legend of Zelda: The minish cap

-Boktai 1, 2

Nintendo DS:

-Advance Wars: Dual Strike

-Advance Wars: Days of Ruin

-Castlevania: Dawn of Sorrow

-Castlevania: Portrait of Ruin

-Lunar Knights

-The Legend of Zelda: Phantom Hourglass

PSP:

-Loco Roco

-Patapon

-flOw (available by download only for those interested)

X360:

-Gears of War 1&2

-Halo 3

PS3:

-MGS4

-Uncharted 2: Among Thieves

-Resistance 1&2

-The Last Guardian

I just finished Red Dead Revolver and Gun, the only two Old West themed games that I know of and I must say that I believe the genre is worth investing in.  Personally I'd like to see something along the lines of an alternate time-line or TechWest sort of game.  Red Dead did a good job of creating an unreal stylized Old West and Gun did a good job of creating a beautifuly realistic open world in which to ride around in.  The game Darkwatch takes Old West technology but adds a flare of style to make some great looking weapons (not to mention Old West Vampires!)  Imagine a TechWest game with Steampunk style vehicles along with horse and buggy.  Imagine being a gunslinger who is part mechanical and for power-ups you get gears and parts to upgrade your quick-draw speed, etc. 

The duck-and-cover system used in Red Dead is a must but so is the wide-open realistic environment of Gun.   The linear confined levels of Red Dead allowed for some stylistic expression (the quick-draw shootout in the train car) and there's no reason a game can't have both.  You could have chase-style battles taking place out on the plains on horseback and close-quarter duck-and-cover shootouts in the town streets, inside buildings, or inside trains, etc.

I'd like to see a Red/Solid Snake looking character with perhaps a mechanical arm or something along those lines.  For anyone who has seen Vampire Hunter D you know how cool a mechanical horse can be as well.  For the antagonists I'd have an eccentric cast of characters (much like the Metal Gear series) and I'd have to include a vampire in an old west suit, tophat, and cape (which of course must be killed with silver bullets!) And following in the footsteps of Metal Gear and Red Dead there simply must be one character wielding a gattling gun (preferably carried in a coffin.)