My order of favorites:
Sean Connery for being the first and best
Daniel Craig for bringing a dark, gritty Bond into popularity (even though Quantum of Solace was a bit disappointing)
Timothy Dalton for a similar reason as Daniel Craig, though not to the same extent
Roger Moore, for doing his best to emulate Sean Connery despite the negative turn the movies took
Pierce Brosnan, for doing nothing particularly spectacular and doing a couple of the worst Bond movies
And finally George Lazenby, for being just plain awful.
EDIT: Actually Goldeneye was a really good one, I sometimes flip-flop Pierce and Roger. But they're both way better than the worst.