Oh my ****ing god. If they manage to make the engine work well on multiple platforms, what makes you think that the PC versions of the games wouldn't run well too? Though, of course the game devs are responsible for it too.
For example: Gears of War for PC looks and runs better than the xbox version.
First of all, you are missing the point, a good console game and a good PC game are two different things, they are different audiences and people want different things out of the games, things that make sense on their chosen platform, and works well with their hardware and input systems, and for this reason, a straight port is never going to be good, it might work, but on the PC it will allways feel dumbed down, and if made PC first and then ported to console, it will feel cluttered and most likely too hard to control.
Cross platform titles are therefor good for buisness, but bad for the gamers, especially the PC gamers as they more often than not are the ones who get the ported version, and since developers know they can make a killing in the console market alone, the PC port seldomly gets the kind of attention from its creators as it should,
Second of all, the GOW pc port was far from succesfull, it is plagued by crash bugs on alot of PC hardware, countless people complain about savegames getting corrupted or deleted, or the game crashing at chapter 3, alot also complain about the game refusing to work at all.
And Epic has done nothing to fix this, nor will they ever by the looks of it.
Similar problems plague UT3, it is incompatible with alot of hardware (like X-FI cards with X-RAM), and alot of people experiance constant crashing, and again, they show no signs of wanting to fix this, infact they actively delete all threads on the matter from their forum.
It seems Epic is incapable of making the UE3 engine work reliably on the PC, or unwilling, the irony here is that its their engine, and others have ported to the PC just fine using the engine.
Needless to say, this does not bode well for any games they port to PC in the future, it may even be a bad omen for UE4 on the PC.