From Russia With Love and Goldfinger. I like most of the Connery ones anyway except for Diamonds are Forever (which isn't as bad as some other ones though).
Thunderball would've been a lot better if they didn't have very long, drawn-out underwater sequences which slow it down. There's a lot of good stuff in that movie and the Bond girls are among the loveliest. They spent so much money on the underwater sequences that they almost felt obligated to show it off, which led to it being far too slow there. It's a bit like the difference between Star Trek: The Motion Picture and all subsequent Star Trek films where they didn't feel the need to have to show off the Enterprise in all its detail in a drawn-out sequence.
Of the Moore films, the Spy Who Loved Me.
Worst ones for me are Die Another Day (worst Bond movie ever), Quantum of Solace, Spectre, Skyfall, the Man with the Golden Gun and Diamonds are Forever. The World is Not Enough is also more boring now than when I first watched it. I don't think it's as watchable on reflection.