Life for an iPhone OS developer must surely be difficult these days: In the wake of the iPad, developers have to choose between having separate apps for the iPhone/iPod touch and now the iPad, or to make their apps universal and appeal to both crowds at once. The issue is even thornier when it comes to gaming.

While the iPad is considered by many iPhone OS developers to be a new “gold rush,” some game developers have instead taken the brave step to rework their existing iPhone apps into universal ones -- meaning that they’ll work great on both the iPhone and iPod touch as well as on the new iPad. It makes life easier for the developers, since they can work on one version instead of creating a separate edition for the iPad.

Customers love it too, since they can buy an app once, use it on all of their devices and be assured of the best experience regardless. Although it may appear at first glance that most iPhone OS game companies have gone the route of releasing separate versions, touchArcade has compiled a list of notable universal games.

Among them: Igloo Games Arcade, a $6.99 “greatest hits” compilation which throws all four of the developer’s iPhone games -- Dizzy Bee, Dizzy Bee 2, Bed Bugs and Flipside -- into one Universal package, rather than updating each game individually. Sounds like a great idea that we’d love to see more of, especially for users who already have too many apps filling our touchscreens.

The others include:

10 Pin Shuffle ($3.99)
Air Hockey ($0.99)
Chopper ($2.99)
Cliffed XL ($1.99)
Implode XL ($2.99)
Isotope ($1.99)
Metal Gear Solid Touch ($7.99)
Parachute Panic HD ($1.99)
Parcel Panic ($0.99)
Strategery ($1.99)
Zombie Attack! Second Wave XL ($3.99)

Hear of any other universal games? Chime in with your favorites in the comments!