xhonzi said:

Also of use here would be the Evil Dead --> Army of Darkness movies. Evil Dead 1 was a fairly straight, if a little quirky, horror flick. Evil Dead 2 was a reboot with a lot more silly thrown in. And Army of Darkness was pretty much a comedy first and a horror (? Mideavil fantasy?) film last.

Can you help me come up with others?

Irregular
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Alien -> Aliens
Evil Dead -> Army of Darkness
Flash Back -> Fade to Black (video game)

Spiritual Sequels
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Final Fantasy Series
System Shock -> BioShock
Blade Runner -> Soldier (screenwriters called it a "Sidequel")

Evil Dead II was more of a full on sequel with a very long recap, than it was an actual reboot. They didn't have rights to footage from the first film, so they refilmed the whole story in extremely abridged form and with fewer actors to save money. In one of the commentaries, Sam Raimi said that you could technically cut the recaps out of each film and edit them together into one long unbroken story. I have often thought about doing this, the only jarring thing would be how quickly Ash would age over that one night that takes place before he gets sent back in time. But yeah, the genre definitely changes.

Another one to add to the video games part are the PS2 games Ico and The Shadow of the Colossus, the later being a spiritual sequel of the former.