Continuing a movie as perfect as "Back To The Future" must have been a really tough job. What made it even harder was that the writers Robert Zemeckis and Bob Gale had to ignore an important character from part one. Because Crispin Glover asked for too much money, his character George McFly, Marty's wacky Dad, hardly appears in the sequels, which constricted the storyline a lot beforehand.
Still, "Back To The Future II" turned out to be a huge success, commercially and artistically. The movie is every bit as clever and delightful as part one. I think most viewers don't realize how extremely complex this story is, because it's so enjoyable to watch. Gale & Zemeckis wrote a screenplay that takes place in three different periods of time, changes storyline more than once, has characters interacting with themselves all the time, but never seems overdone or confusing. The most original trick the two Bobs pulled was to virtually return to part one and have the main character interfere with the original storyline. I don't think that has ever been done before or since.
No, the movie isn't flawless in a sense that everything can be explained logically. Bob Gale admitted himself that Marty and Doc shouldn't be able to visit their future selves in the first place. There are a lot of impossible time travels in part two (you can read about them in detail here: http://mjyoung.net/time/back2.html). "Mistakes" like that don't take away any of the fun, though, and I still think that the "Back To The Future" trilogy incorporates the logics of time traveling better than any other movie ever did.
Besides the perfect script the trilogy's success is due to Zemeckis ever so beautiful direction and his eye for detail, and of course the great cast. Michael J. Fox, Christopher Lloyd, Thomas F. Wilson and Lea Thompson, all shamelessly underrated actors, are once again brilliant. It's a REAL pity that Crispin Glover didn't return for the sequels, but as I've said before, Gale & Zemeckis did a great job writing their way around his memorable character. The only other actress that didn't come back was Claudia Wells, who played Jennifer in part one and was appropriately replaced by Elisabeth Shue here.
Summing up, "Back To The Future II" is a more than worthy follow-up to one of the best movies of all time. In fact, I think it's the best sequel ever made, only rivaled by "Terminator 2: Judgement Day". But that's a different story...
