There are a few 3d spaceship games like Galaxy on Fire, StarPagga, and Station Defense but they're dogfighting games without discrete levels like Descent. They're more like Descent Freespace or Wing Commander or something; you fly around in empty space for 45 minutes shooting at little radar blips with pew pew lasers and generic missiles as opposed to Descent where you go through different levels fighting all sorts of enemies and using fun weapons.
There are also lots of 2d space shooters ranging from dual stick games to scrolling shoot em ups to variants on asteroids but I'm assuming you want a 3d, 1st/3rd person spaceship game if you're looking for something like Descent. The best 2d spaceship game on the app store is Space Miner: Space Ore Bust.
Last edited by Advancedcaveman; 09-14-2010 at 12:47 PM.