This is my personal must-buy list. They are all iOS exclusives, and most of them will last you hours for a minimal investment. There are more of course, but this is my definite AAA must buys.
100 Rogues - An awesome top down rogue-like RPG. I bought this last week, and I regret not knowing about it before. Re playability is through the roof too.
Dungeon Raid - A match 3 game with an RPG meta-game. It isn’t like Puzzle Quest though, because you always see the board, and the enemies are just tiles. Easily one of my favourite games EVER.
Super Quickhook - Platformer where you need to use a grapple to go though levels. It is easy to control, and it has light RPG mechanics in the shape of an item store with upgrades.
League of Evil - It is like Super Meat Boy. Need I say more? Probably the best example for on screen buttons. The magic secret is that there is no momentum, so the controls are really tight.
Space Miner - I played the entire campaign when it came out and it took me 6 hours. Another shining example of virtual controls done right. Instead of a dpad or fake analog stick, it is a wheel that you steer. It is basically astroids with missions and an upgradable ship.
Super Mega Worm - You are a giant worm that need to eat people. You level up and become more destructive. Charming 8-bit style combined with hyper violence is always winning.
The Incident - Objects fall from the sky and you must tilt your iDevice to avoid them. Hard to explain the charm, but it is really good.
Infinity Blade - With the new content update, I have no trouble recommending it. Punchout with sword.
Rage HD - An on rails FPS with an awesome score and combo system.
Tiny Birds - This game is number one on the app store for a reason, it’s really good.