It's an old cliche that the book is better than the movie, though there are some exceptions.
here's a thing i posted somewhere
It's almost guaranteed that a sequel will be viewed as worse than its original, if the original was well-received. People will say things like "it's missing some of the qualities I really liked in the first movie", when really what people are saying in their heads is "it isn't literally the first movie". Having something original pumped out gives people the standard of "I liked this" and those memories become locked in to how you view that piece of media. When a sequel comes out and it's anything different even if it tries to be the same, you go "hey that isn't the same thing I felt before" and reject it. The same thing happens when a book is made into a movie, and it's probably a more commonly heard complaint than sequelitis: "the book was better".
In regards to original movies that end up with sequels, they're often originally written as a standalone piece. When the creator works on a project that is really segmented into parts, the next movies flow so naturally that you often don't call them sequels. Like the Chamber of Secrets isn't the "sequel" to the Philosopher's Stone. Using the term "sequel" is almost always reserved for movies where they didn't actually write the first with the second, or even have a second in mind at all. Because of this writers have to go back and sort of try and find what people liked about the first movie and abnormally inject it into the second because "that's what people liked". The same goes for games.
You're also stuck if you copy the original too much, because then it becomes obvious and people spot that. This is a bigger problem in movies, since games being formulaic isn't necessarily a bad thing if the concentration isn't really on the story, then it's an activity people enjoy doing rather than just getting things fed to you. If you aren't writing a second movie together with the first, you're boned by doing things different and you're boned by doing things the same. People probably won't like it as much. What you can do is bring something entirely different to the table, and throw away the opportunities for people to compare the first and the second. You have to be able to get the essence out, and invest it in an area completely unlike the previous. Diversity is a fundamental key for good writing.
The main issue here is that sequels are called that because they have the same characters and general setting. People are attracted to sequels because they've associated their feelings about the first movie with the characters rather than the writing and other elements that made that movie what it was. If you just made entirely different movies, people won't get that instant attraction to it from the characters. It's also technically easy to use the same characters and everything for a new production. If a production studio doesn't have a solid reputation going for it, the most lazy and profitable option is to make sequels. If you're Studio Ghibli, you don't give a shit and just make whatever you want: people associate the movies largely with the quality the studio offers, not the characters. Sequels are unnecessary at that point. Same goes for what Studio Trigger has going on right now. Basically, the solution to sequels is either to write multiple parts at once to tie them together well, or to become so awesome and varied that you get a reputation for your work rather than the work getting a reputation.
Not that it necessarily applies, you just reminded me of this
