That would depend entirely on the underlying game engine, how well threaded it is, and how core speed depended it is.
Generally speaking though, Intel has AMD beat.
Edit:
You are saying "more powerful cards" as in graphics cards? If that is the case, then AMD as Intel currently have no discrete graphics Cards.
Also you really have to be more specific, what games are we looking at, older games only utilizing one or two cores, new multi threaded games, are we looking at power consumption too, price, upgradeability of the platform of choice, really need to set some criteria for the comparison of brands.