Are PCs good for gaming? The short answer is yes, Tim Sweeney (of Unreal fame) is wrong because computers play many of the best games the platform has to offer without much struggle. Games like The Orange Box, Guild Wars, World of Warcraft, The Sims 2, Company of Heroes or The Lord of the Rings Online all run fairly well without too much muscle behind them.
His primary complaint (and ours too, actually) is that integrated graphics chips which are installed on the computers that stores like Best Buy sell, are in no way capable of playing the newer games sold at the very same stores. Intel is largely to blame for this, but of course if you've ever looked into buying a brand new video card, then you know they're not the only culprits of PC gaming's issues.