CutiePie2000, I've got to say that I think Vancouver's logo is MUCH MUCH MUCH better than London's. At least it evokes native culture/the Pacific NW to me. London's doesn't really evoke anything to me at all except the early 90s and neon fanny packs.
I lurk at Olympic discussion forums and the consensus is that the London logo is one of the most hated ever. Especially by those from the UK. The worst part is that some animation from the London Olympics website revealing the logo back in June 2007 evidently caused seizures in some epileptic individuals. Here's a rundown:
http://en.wikipedia.org/wiki/2012_Summer_Olympics#Logo
So I think Vancouver is definitely sitting pretty with their logo.
Other notable logos... hm... I really liked Sarajevo's, Nagano's, Seoul's, Atlanta's (though it now looks particularly dated to me), and ESPECIALLY Athens's.
The worst thing of all by far though, was Atlanta's awful, awful, awful mascot Izzy.
Fun graphic of Olympic mascots:
http://en.wikipedia.org/wiki/Image:Olympicmascot.jpg