Do Sequels Stink?

I've been perusing the worst to the best list of movies made from Comic Books.

As much of a fan as I am of these movies, there have truly been some stinkers, as you will see from the first films. Rather than debating them, I was keen to look at the general perception that sequels are usually a quick cash-in on the dwindling success of the first film. According to this list, arranged from review scores (not necessarily anything to do with box office sales, mind you) there are several franchises where the sequel has rated better than the original.

Addams Family Values > Addams Family
Batman Returns > Batman (and Batman Begins beats them both)
X-Men 2 > X-Men (but however, > X-Men 3)
Spider-man 2 > Spider-man

With a bunch of sequels coming up (The Dark Knight, Hulk) it will be interesting to see how they fair. BTW, where was Fantastic 4: Rise of the Silver Surfer in that list?