Probably 'Another Way To Die', Jack White's duet with Alicia Keys from the previous Bond film, Quantum of Solace.
Have to say, personally, Skyfall is the best Bond song of the 21st century, best one since The World Is Not Enough. Perhaps that's not saying much, because I found Chris Cornell's 'You Know My Name' to be utterly forgettable and Madonna's 'Die Another Day' was awful.
Oh, I rather liked that - it's one of the few Bond intros that I actually watch instead of fast-forwarding through. Mind you, that might be because the graphics are so brilliant.
As for Adele's offering, I haven't heard it all the way through but it does sound rather over-blown and turgid and she sings in a most bizarre accent.
I remember one of the posters over on the film board confidently predicted months ago that she'd not only get nominated but win the Oscar so I'll be interested to see how it pans out.