Sean Connery: undoubtedly, no matter what has been said and the comparisons, the Scot is the best James Bond of all and the one who, in Dr. No, made Bond eternal. He is James Bond. Any one who has read Ian Fleming's original books, will agree that - of all those who have portrayed the character on screen - Sean Connery fits it best and does the best depiction: suave, cool, cold-blooded and smooth. Of all Bond movies, it is in those that had Connery that are most unforgettable with the most unforgettable scenes: right form Dr. No with the opening scene of three blind men crossing the road; to Honey Ryder; to Pussy Galore; to Auric Goldfinger in Goldfinger.
Timothy Dalton: an excellent actor who played the Bond role very well and very seriously but, in a way, Dalton didn't seem to fit in well as Bond. Still, it is unfortunate he didn't continue. Other wise, he was as good in portraying Bond as Fleming imagined it; as Connery did. He, like Connery, as Bond, was serious and yet cool and very charming.
Daniel Craig: he is good. But, his stunts are too unrealistic and too 'digital'. Craig is not that good an actor compared to Connery or to the thespian - Dalton. Watch him being interviewed in person and him as Bond - there is a very slight change, if any. Craig is the most real, most ruthless and cold blooded Bond ever; though he might fit in with what our imaginations visualize Bond should really be like, he lacks the charm and sophistication that Connery or Dalton have. He would have been more suitable playing a bad, ruthless villain in a Bond movie.
Roger Moore: had the sophistication, the charm and the suaveness of what we imagine Bond to be. But, he lacked the coldness and the ruthlessness that a spy like Bond was supposed to have. And his Bond movies, which are supposed to be serious, were too full of comedy.
George Lazenby: remember him? The Australian, as much as he tried, looked ridiculous portraying James Bond. But then, had he done more Bond roles instead of only that OHMS, Lazenby might have done better and, maybe, would have been remembered differently.
Pierce Brosnan: most probably the worst Bond ever. He didn't fit in the roles and he shouldn't have played them. He seemed too good, too nice and too pretentious for the role.
Barry Nelson: is the first to have portrayed James Bond way back in 1954, on screen, on a low-budget, black and white television series 'Casino Royale'. Reportedly, Barry played James Bond very casually, and despite several laughable fighting and torture scenes, the episode was an interesting and enjoyable rendition of Casino Royale.
Other James Bond renditions: In 1956 Bob Holness provided the voice for James Bond in a South African radio adaption of the Ian Fleming novel Moonraker. In 1967 David Niven plays a retired James Bond in 'Casino Royale'. And did you know that - In 1964, between playing Simon Templar on The Saint, Roger Moore starred as James Bond in an episode of the comedy sketch show Mainly Millicent? In 1973 Christopher Cazenove played James Bond in Omnibus: The British Hero, a documentary and literary review style show on the BBC.
It is reported that, Ian Fleming envisioned James to be like Hoagy Carmichael - but cold and ruthless. And he wrote the Bond novels with Cary Grant in mind; Grant was initially offered the role but turned it down. Imagine if Cary Grant, an American and a bisexual (or was he homosexual?) had taken up the role and had been in that first 'Dr. No'; Cary Grant playing the very English, macho character - where would James Bond be today? James Bond would have taken a complete different course. It should also be noted that, the Bond films, although trying hard in portraying the character as Fleming imagined him, are not how Fleming portrayed them in his books. Like the James Bond movies or not, one thing is certain - whoever has been in a James Bond movie, as him, as the/a villain or as a 'Bond Girl', has gone down in history and been part of one of the best and most successful movie merchandises, internationally, of all time.