Batman Returns was disappointing as a sequel but seems to age pretty well. Compare it to the 2 that followed it, and it's high art.
My list looks like this:
(One I waited for what seemed like forever for, only to be disappointed on every level)
(Whack. French. Suckfest.)
(I really honestly thought Reloaded was setting up mindblowing revelations for the 3rd movie, only to have pt3 make not only pt2 suck completely, but annoy me into hating everything about anything Matrix)
Return of the Jedi
(You know, this movie is aweful. I find more about it that I hate every time I see it. It certainly sets the tone for the PT - childish, vapid, and hacky)
(Imagine a Robocop sequel with the director of ESB at the helm! But now imagine a kid drug dealer, a robot addicted to smack, terrible music, a complete lack of subtext and humor from the first film, and Robocop's costume looking like blue plastic. Suckfest)