Moore's portrayal of Bond was the truest to Fleming's original character.
The character of James Bond was originally created by author Ian Fleming, who based the spy on some of the actual secret agents he knew during World War II.
Moore's Bond was an intelligent, gentlemanly Bond, more of a sophisticated detective than a fist-throwing, explosion dodging, guns blazing, muscle-bound thug, exactly as Fleming described him in his book.  He was a bachelor, very available to women, but not available for long-term relationships. Moore captured this perfectly. It is believed in some circles that Ian Fleming wanted Moore to play Bond from the beginning, and the writer and Bond creator was reportedly very pleased when Moore finally stepped into the role. 
Moore was an awful actor. He even confessed himself that his entire range of facial expressions was limited to three, “right eyebrow raised, left eyebrow raised, and eyebrows crossed when grabbed by Jaws.” Even his idea of “cool” and “sophisticated” came across as spoofy and damaged the Bond brand. Sean Connery even accused Moore’s Bond of being “a sort of parody of the character.”  Following Moore’s portrayal, writers had to get Bond back on track and make the character realistic and tough again. That is why they cast Dalton, who brought a heightened level of realism and attempted to shed Moore’s fantasy, goofy, pun-laden image of the character by adding a layer of psychological intensity.
[P1] The best Bond is the Bond that remains true to the original work. [P2] Roger Moore's Bond is closest to Ian Fleming's work. [P3] Roger Moore is the best Bond
[Rejecting P1] Fleming's character was tougher and more sophisticated than Moore portrayed.