Any title which uses deferred rendering (which is actually much easier on the PS3 than the X360... probably the only thing that's easier, but its a big, big deal) is going to surpass a title which doesn't, this gen. It increases the effective performance of the PS3 GPU by a truckload.
The X360's memory architecture actually makes it pretty difficult to do deferred rendering. Thus PS3 games can do all sorts of fancy pixel shader stuff in just a single pass -- yielding some pretty nice looking scenes, at a decent framerate. The X360's flexible GPU is, in pretty much all regards, somewhat superior to the PS3's RSX, but this particular rendering technique really turns the tables in a big way.
It takes some skill to implement properly though, so you're not going to see it in cross-platform games, unless the developer wants to spend a truckload of money making the PS3 and X360 versions a lot different (i.e. delayed ports could maybe do it, but often don't anyway). "Superior graphics" pretty much applies to PS3 exclusives only, for this reason. That being said, the PS3 does have an awful lot of big exclusives coming in 2009.
