Someone already made the point that Amazon's official reviewers often seem entirely out of step with their hordes of unofficial ones. This movie is a great example. It deftly avoids pitfalls that sink other films and does so seemingly effortlessly. It gains so much in sublety that it falls beneath the Hollywood radar of critical acclaim.
First, here's a film that delves into the real entanglements of time travel, but unlike Back to the Future, keeps it light. George Carlin plays himself, a burnt out hippie in the role of enlightened visitor from the future. Like Jeff Goldblum, he always plays himself, only the scenery changes-- check him out as the priest in Dogma (which is not at all a family film). Keanu Reeves does a great job in this film which, if it falls in the Doofus Duo genre, is at least as good as the Wayne's World and Dumb and Dumber films.
It's also cleaner. Anyone can write a dirty joke; try writing a clean one. This movie is full of them. Chesterton said it's harder to write a joke than a sermon. Obviously that's why there are so many (bad) sermons. This film succeeds with both good-natured humor and the light-hearted message of "Be excellent to each other." Has the Golden Rule ever been put better?
Why is this film so much better than its sequel, Bill and Ted's Bogus Journey, which has an excellent if unrealized story line? Because all the special FX budget was spent on the "hell" sequence in that film, which bogs down the rest of the picture. There's a most excellent line of comic books that accompany the Bill and Ted saga, by the same artist who did Milk and Cheese. The story arc is both humorous and gripping. This is one of the few properties that really could deliver a few sequels and works well as an animated series. I join hundreds of reviewers who love this film in recommending this most excellent DVD.