you know I have been thinking about sequels on and off all week and I started at the position that sequels are only ever a necessary evil to get more out of an intensive creative effort, there are some sequels I like more than the original media. the geller examples are good too but haven't personally played 'em :P

but maybe people wouldn't really consider these sequels though... transistor to bastion, majora's mask to ocarina of time, frog fractions 2 to frog fractions, apollo justice: ace attorney to phoenix wright: ace attorney. I think what's common between these is like taking a bunch of resources and processes and making them common between sequel and original work while make a whole other part completely different.

maybe, or I'm trying too hard. Hades II/Hades has about the same similarity as the ace attorneys but one sequel I think is trash while one I think surpasses the original (pending a replay)