What is the best way to develop a mobile application that run on multiple devices mainly (android and iPhone)?

1) Use android frame work and iOS framework.
2) Or use a cross platform development library something like (AirPlay SDK for example).
3) Or there is other way else you prefer.

Please feel free to give me your suggestions.

Edit: I forgot to say, it'll be a game which require a lot of 2-D graphics.

Solution

write your common code in C++, both platforms support it. for platform dependent code you can create one interface with two different implementation