Screen layout is a solved problem on the PC side. Hardware performance, and I'd imagine some GPU quirks as well, not so much... and in that sense, Apple certainly has an advantage since there's a single spec per generation (although a pretty long trailing edge of generations, on either.)

From my end, I don't really see either iOS or Android as a good gaming platform; touch screens suck for serious gaming since you lose a lot of visual area to on-screen controls, and they're wickedly imprecise. Further, nobody seems to be willing to pay console/PC game prices on phones, which means they won't support the same quality of titles (on their own) as consoles/PCs or even gaming handhelds (which already have to have cheaper games.)

That said, while I don't personally get the appeal, there sure seems to be plenty of money to be made on both casual games, and porting older titles back to the phone market.