One of my biggest pet peeves is when the hero and the girl spend a whole movie developing their romance and get their happy-ever-after, then spend the whole sequel doing it all over again because of a stupid fight or other contrivance that separated them long enough for them to start seeing other people.
You know, Hollywood, some people DO develop lasting relationships that don't fall apart when the guy farts in bed. Some people do stay together longer than Britney Spears and her husbands.
I think that's why I liked that Dragonlance series of novels so much (Knights of the Crown, Knights of the Sword, Knights of the Rose, I think they were): the romance start in the first book and those two stayed together, in love growing together in each subsequent novel. No romance re-hash there!