When it comes to Hollywood, the first question that gets asked when a movie does well is how to turn it into a franchise. Sometimes, the material justifies its sequels (we're looking at you, John Wick). However, there are just as many franchises with only one good movie in the whole series, and it's often the first.
There are a lot of reasons a great film will often be followed by a slew of lackluster follow-ups. Often, it's because the sequels are just baseless cash grabs with no heart. Other times, it's because the premise of the original is so unique and high-concept that it simply doesn't leave room for sequels - and yet the producers don't let that stop them for a second.
While some over-stretched franchises have amassed legions of devoted fans and others are somewhat universally considered to be cinematic failures, the fact is some film series would have done themselves a favor if they'd quit after their first installment.