Angry Birds

Angry Birds epitomizes what an iphone game should be.  Simple intuitive controls, gameplay that can be entertaining for 60 seconds and for 60 minutes, and replay value. 
 
The basic premise of the game is you launch different types of birds from a sling-shot at structures made of wood, ice and stone holding different types of pigs, and the object is to destroy all of the pigs and get the highest score possible.  There is a definite element of strategy in order to destroy the structures and the pigs in the most efficient manner possible to get the highest scores, and the game rates your performace for successfully completing a level by giving you a rating of 1-3 stars. 
 
The controls utilize the touch screen interface, without feeling gimicky.  You "pull back" on the birds in a sling-shot to aim and gage the power at which to launch them.  You release your touch on the screen to hurl them towards the structures in which the pigs sit. 
 
From there the physics dependent on the type of bird vs. the type of structure determines what happens next.  The designers have taken great care to make sure that each level presents its own unique challenge that can be solved in more ways than one in many cases, but only one way in others.
 
The simplicity of the game makes this a game that you get into instantly, and the scoring system and achievements ensure that you can get hours of entertainment and replay out of the 165 levels they have included and continue to add to with each update.  Angry Birds is easily my favorite iPhone game to date and definitely one of the best values.