I would like to have a game prototype tool that can build a game prototype very quickly so that I can test and prove my game ideas. The key is quick to build. Can you suggest such tools or ways to build a game prototype fast?
GameSalad and Unity, probably SIO2, too.
I would strongly suggest not to focus on the iPhone per se, You can get away prototyping on the Mac with BlitzMax, testing everything out and ONLY port the things that have proven good to the target platform.
No need to limit yourself right from the beginning.