I think it's largely a generational thing...
I'm 27 and hadn't seen any of the Star Wars movies until about 2 years ago. I also hadn't seen any of the Harry Potter movies until a few months before Half Blood Prince was coming out. Then I cracked when I got Netflix and went through them all.... The results for me?
Star Wars: Other than Yoda, I didn't really like them that much. Especially the old ones, but I have a weird thing with old movies UNLESS I was into them as a little kid. I just can't stand old movies, the look, the acting, everything... The newer ones also didn't help much for me. Some parts were cool, like Yoda fighting the old guy, and pretty much anything else Yoda.
Harry Potter: I love them, oficially got hooked. Just all around a very cool set of movies for those who like escapism. Good acting IMO as well. Obviously the first couple were a little corny at times, but they're little kids so they get a pass.
Twilight: Kill me for admitting this, but I find them entertaining. The fans are annoying, but you can say that about any die hard fans of anything (can you say APPLE???) Tweens just tend to make it ten times worse.