Although many will tell you that this is the best adaptation of Alexandre Dumas' story, those people probably haven't read the book. Yes Richard Lester's film has a lot going for it and gets a lot of things right, it also gets a lot of things wrong not only in terms of staying close to the story but also dramatically.
The cast, for the most part, is spot on. Oliver Reed steals the show as Athos and proves to be perfect casting for the role. Heston's Cardinal, Dunaway's Milady and Lee's Rochefort are all brilliant. Unfortunately, Raquel Welch proves to be this film's splinter which refuses to go away no matter how much you try to take it out. Her performance is absolutely abysmal and the director's decision to turn Constance into a bumbling clumsy fool is unnecessary and frankly DUMB. Whatever happened to the Queen's cunning spy maid? You know when you've been Clouseau-ed. Michael York is fine as D'Artagnan although once again Lester makes the character a little more bumbling than he needed to be.
The film basically suffers from too much comic relief. As if the book wasn't funny enough, which it was. It's like the Monty Python gang read the Three Musketeers and added a whole bunch of inappropriate jokes everywhere. It just doesn't do it for me. Maybe the problem is that the humour is much too English and it feels awkward in a French setting.
The action is very clunky and messy but I think that was a conscious decision to keep the fight scenes somewhat realistic. Give me Gene Kelly's cartoony acrobatics any day over that, though.
Overall, it's ok and some of the cast members alone make the film worth watching but if you're a fan of the classic story and are expecting an exciting, faithful, definitive adaptation of Dumas' story this is not it.