Oh wow man, at first I checked out iBuyPower and was kind of like "meh seems confusing" (on account of weird setup of the site) but actually it makes it pretty easy for a layman like me. Only thing though, do you know, or could you ask your friend if he paid attention to the meter on the side that tell how good a selected game will run? I just want to know the legitimacy on that.
I've no idea, but I know he had his rig built to play Star Wars: The Old Republic. I built an almost identical rig, minus the liquid-cooling, and included a better video card in order to run Skyrim. Either way, I'd suggest visiting the official forums for any game you want to play to find out which configurations work best. Some older games will not play as well as newer ones on today's top end rigs. There are a variety of reasons for this, not the least of which is the extensive use of hyperthreading. Oblivion, for instance, made no discernible use of multi-core processors, meaning my top of the line Pentium D purchased specifically to run Oblivion hurt me more than it helped. In the same way, the new quad-cores wouldn't offer any real performance boost either. Every game, indeed every application, is unique in how it is configured to utilize system resources. Consequently, some "upgrades" people make to improve the experience have no real impact. Another example, Skyrim doesn't really benefit from have 16gb of memory as it's not setup to make use of it. So, again, I suggest researching each game separately in order to see what system specs would best run it.