It's been a long time since I watched the Bond films (about 15 years), but the three that stood out the most to me at that time were "From Russia With Love", "On Her Majesty's Secret Service" and "The Spy Who Loved Me".
I think it's a great shame that Lazenby never played Bond again.
I've heard nothing but good things about it. I won't be watching it until I've finished watching all the others, including the two unoffcial ones, "Casino Royale" (1967) and "Never Say Never Again".