I only have an Omni10 rather than Surface Pro/Pro2 but although the 2GB RAM on my tablet is a limitation, the lack of touch interface for the vast majority of games is a
much bigger deal.
Adding a mouse and keyboard via USB will solve most issues, but that kind of defeats the whole point. So far I've managed to run Bejewelled (no surprise there) and Age of Empires 2 successfully. Many others start up fine but you soon find the resolution's all messed up, or the mouse pointer doesn't work properly even with a USB mouse attached, or you can't get back to desktop properly, or...
It's a shame. Seeing Doom3 or the Walking Dead load up fine, but then fail to navigate properly is frustrating. Not that I planned to play either, but it's interesting to explore what's possible*.
Ultimately I bought my Omni10 (£250) for a simple but specific desktop task which works well, so I'm not complaining (well, not much :->). I'm just not as impressed by the overall desktop mode use as I'd hoped. One particular annoyance is the way that when in Metro mode the keyboard automatically pops up when you tap to enter text. In desktop you have to bring it up manually, and that seems like a strange decision. I mean, under what circumstances would you tap in a text entry box and not want to use the keyboard?

At the very least it should be an option.
Overall these are interesting devices. But the longer I own this Omni10, the more I think a Win9 tablet might be the thing to buy. If I didn't have a particular task in mind, which neither iPad nor Nexus7 can accomplish, I'd have been tempted to send it back... though I will admit to being impressed, overall, by the Bay Trail processor's capability. This thing could easily be my main PC for everything except gaming, and a totally silent one at that.
*I've also failed to get Sine Mora, Torchlight II and Return to Castle Wolfenstein to work, though iRacing does! Driving a hardcore sim with one finger is something of a novelty.