Michael Lonsdale and Louis Jourdan remain two of my all-time favorite Bond villains, even though the movies they were in were pretty awful.
On Casino Royale: A great movie, almost completely destroyed by changing Baccarat into Texas Hold-Em. Bond may as well have ordered: "Beer. Canned, not bottled."
Biggest waste in the series: Eliminating Felix Leiter from the franchise during the Brosnan years (and replacing him with Joe Don Baker and Michael Madsen).