Gameindustry.biz has a great article on the main issues concerning mobile game developers at the Mobile Games forum held during this years E3 Expo. The problems include the high costs of porting to so many handsets (which can even cost more than the original development of the title), and that porting has become a necessity for phone carriers...
"Mobile game developers face the tremendous challenge of how to get their games to work on over 250 device platforms serviced by more than 80 different mobile operators and in numerous languages. As Bhatia described, "game publishers develop a game from start to finish, but only for a basic handset, oftentimes a Nokia Series 40 or Series 60 phone. Of course, no carrier will promote a game until it works on the majority of handsets they are selling in the market. Therefore, the game is not marketable until it is 'ported' - adjusted to work properly - on all the carrier's handsets."
The article explains that outsourcing porting work is a solution that needs to be tread carefully...