8-bit vs. 16-bit is a standard arcade shooter (in which you take down enemies as they fly at you on a 2D screen) with one very meta twist: You can flip back and forth between an 8-bit (as in, the old NES and Atari-style graphics) and a 16-bit (like a Super Nintendo or Sega Genesis) mode at any time. Not only does that change the game's graphics and feel, but it also makes enemies from that era give extra rewards when killed in the same mode, which means you can get higher scores by switching around at the right time.
The gameplay is lots of fun, and while it's relatively spare, the two different modes provide a bit of originality, and a lot of room for trying to master your scores. Game Center integration provides a little competition between you and your friends, and of course Retina Display graphics show both retro modes clearly.
8-bit vs. 16-bit provides a nice trip down two different memory lanes, and combines some original gameplay with two very different graphical styles. Retro game fans can pick it up from the App Store for US 99 cents, or try out the free version to see what it's like first.