I wish I'd have seen Brokeback Mountain so I could vote in this. So instead, I'll just bring up some points:
Outside of not including Q, Moneypenny, "shaken, not stirred", and having the gun barrel show up as the very first thing (though its understandable as it was a reboot), Casino Royale was pretty much a perfect Bond film. Bond was finally back to being the cynical asshole that he usually is. We only saw glimps of this with Brosnan (though I do think he did a good job as Bond) and Dalton and Connery kept true to it, but Moore and Lazenby didn't at all. The film's villain is believable (outside of the weeping blood, but at least that's better than having metallic teeth), the women had a purpose instead of just being thrown into the plot for no reason other than T&A, the action was forceful and gritty, so on and so forth.
So while I won't be voting, as its not fair for Brokeback, I urge everyone else to vote for Casino Royale.