I agree about the excellent quality of the first film. As someone old enough to remember the era depicted, I got a real kick out of some of the jokes--the "super service" at the gas station, the dismay of the fountain guy when Marty asks for a "Pepsi Free", Lea Thompson concluding that his name is "Calvin", and one of my all-time favorite bits of movie dialogue:
Doc: If you're from the future, who's the President?
Marty: Reagan. Ronald Reagan is the President.
[long pause]
Doc: Ronald Reagan? The
ACTOR???? And I suppose Jerry Lewis is the Vice President!
I love this because it underlines how absurd this notion would have been in the 1950s. (Don't get me started about how someone as dimwitted as "Dubya" would never even have been a viable candidate in, say, 1956...)
There were also cute things in the 2nd film, and in the "Western" film.
Since we're recommending other "time-travel" stories, one should definitely investigate Robert Heinlein's "All You Zombies" (considered by some connoisseurs to be the best "time-travel" story of them all) and the excellent film "12 Monkeys":).