Personally, I'm not much of a gamer (although from time to time I'll get caught up in something). That said, I don't see the appeal of staring at a 4" screen for hours gaming with minimal controls (tilt / multi-touch).

So, for a phone sized device, I really think service (carrier), screen size, battery, other options, are going to come before cpu/gpu choice based on games available. My phone is mostly used for a time killer, and games should be easy to start and stop quickly, nothing too involved. Difficult to stop in the middle of a mission when the line moves faster than you expected and it's suddenly your turn.

Tablets are a little different. To me they still suffer from a control problem. I'd think a well done graphically intense game would benefit from a gaming controller with multiple joysticks, buttons, etc. The bigger higher res screens on tablets would be great, but for gaming you may not want to hold the extra weight for an extended period of time. So, you'd probably set it down, and need a controller. For me having to take a controller along reduces the portability (and possibly charger).

I'd guess a smaller percentage of people would buy based on available games, but I'd bet the majority are going to be more concerned with apps in general and media capabilities (playing hd video, tv out, sound quality, etc) and perhaps productivity (office) type apps.

I'd be more likely to buy a tablet with a particular cpu/gpu if it had a specialized linux distro compiled for it that took advantage of a particular cpu/gpu combo. Either as a dual boot or an app/vnc session.