[foobarrio]

The games are there, you just have to dig. Phones and tablets lend themselves really well to bullethell and other shmups(of which I love):

   * .Decluster
   * DoDonPachie, DeathSmiles, really anything by Cave
   * Shogun: Bullethell

They have also done remakes of popular shmups like R-Type and popular Neo Geo shooters. There is plenty of depth in and fast action in these games. Tapping rhythm games are awesome like:

   * Rhythm Control 2

There's also adventure games:

   * Sword and Sorcery 

Not to mention the Secret of Monkey Island series and Grim Fandango have been remade for iOS. I also know a guy was super into Street Fighter tournaments and really like Street Fighter IV on his iPad. The platform has already been proven as a viable gaming platform. Very few people other than serious gamers want to pay more than a few bucks for "just an app".