The only movie sequel that comes to the top of my mind for this question is Back to the Future Part II. I really enjoyed the 1980s vision of what 2015 might be, especially now that we're less than four years out from the real 2015.
I know it's not really a conventional reason to enjoy a sequel over an original movie, but it's still really fun to compare the movie with reality. That's what made BttFII so much more memorable than the other two movies for me. :)