Don't try
Don't even try and play games on Virtual PC. It's slower than a snail on drugs 😛 . You'll be lucky if you don't pull your hair out waiting for the start menu to pop up after clicking it, it literally can take 5-10 seconds for it to appear after clicking. Now this is coming from experience on a 700Mhz G4, so 1.25ghz should be a little faster but still nowhere near the speed necessary to play games on more than 10fps, and thats wishful thinking.
Virtual PC 7 should be out soon, and rumor has it that it has native Video Card acceleration rather than having to emulate it in the current VPC6, but it still needs to completely emulate an x86 processor (as you'll find in the humble wintel). In other words, not very much faster, and with a 32MB card in the lower end of the market like an eMac hardly any noticeable difference at all. Buying a bucketload of RAM might help though.....
There are two ways to get around this:
1. Fork out a few hundred and get a cheap/fast PC box, or even a console.
2. See if any of your games are available for mac, cos if they are you'll be fine and dandy. On the other hand if you already own all your PC games I don't think you'll want to be forking out all you hard earned again...
Hope I was of some help, sorry to burst your bubble. 🙂