It depends on whether I consider the sequel too unnecessary (like if the original story came to a good and definitive end) and mainly whether they actually put as much effort into it as they would an original movie. Too often people coast when doing sequels, because they know they have a built in fanbase so they feel they don't need to try as hard.
I tend not to like sequels, but when the filmmakers actually put the effort in to make it good, and it isn't at odds with the original I can like them a lot :)

Mermaid-tail Great comment

depends on the movie

agree with Mermaid-Tail ^^

Ice Age is an example of sequels I hate. Toy Story is an example of sequels I love.