For iOS I like:
Blue Libra 2
I don't like autumn dynasty. I know many people do like this game (Szei has posted multiple times about it) but I think it's almost too complex for an iOS device. The game requires lots of speed, like Starcraft, to be good. I can't really play that fast on an iPad so I would say that I would prefer such a game on a PC.
Mushroom wars is casual fun but I think it works better on iOS and seems more intuitive to me. Blue libra 2 is also very fun but no one plays it :/