Battlefield 3, definately.
Then I'll get Skyrim around hopefully the same time.
However, due to Battlefield 3 being the distinctly shorter of the two, I'll play that first.
MW3 can wait until it's £25 or less, now that I saw some gameplay of it.
At least Black Ops tried something different with the story, and in my opinion, pulled it off. MW3 just looked like minimum effort had gone in.
That bit where you drive a Zodiac boat through wrecked ships? The guy in front had the exact fucking same animations that Captain Price did when you drove the boat as soap in MW2. Fucking ridiculous.
Contrary to the worldwide norm, I bloody dispised Oblivion. It was awful in nearly every sense when I played it, and I'm genuinely puzzled as to how people rated it so highly.
Skyrim, however, seems to have fixed everything I hated about Oblivion, and then done more.
I think it's worth getting for the Dragon fights alone, but then the animations looked so well done, and the combat looked far less like total shit and much more like fun and badass.
I still think Battlefield 3 is going to be better than both, to be honest.