Instead of humor, it may actually be the perfect ground for research.
First, I will say that exceptions are everywhere, but in most cases you can see the similarities and highlight the rule.
1) OG. First parts of films. Perhaps these are not ideal films, but they are made with all possible soul, because the creators did not know - will there be an opportunity to make a sequel? They also have a complete plot and idea. Expamples: Alien, Terminator, Jurassic Park, Matrix, Robocop; or, if we take franchises that are measured not by individual films, but by whole triquels - Star Wars Original Trilogy, Lord of the Rings trilogy (part of middle-earth franchise).
2) Sequels. In general, they don't have to be sequels, they can be prequels or sidequels. In any case, they are made right after the OG. Typically, these films are more ambitious, bloated and polished. Perhaps they lose a piece of the author's enthusiasm or atmosphere for the sake of the box office. They may be "softer" compared to the originals, but that does not make them worse overall. Examples: Aliens, Terminator 2, Jurassic Park 2, Matrix 2, Robocop 2; or Star Wars Prequel Trilogy and Hobbit trilogy.
3) Triquels. These are perhaps the weakest films in the franchises. Everyone has known this for a long time. The reasons for this: running out of ideas or laziness and the desire for easy money on a popular name. Very often these films destroy everything that was created before them and, in general, can ruin the franchise. Of course, there are exceptions, but they are rare. Examples: Alien 3, Terminator 3, Jurassic Park 3, Matrix 3, Robocop 3, Halloween 3; and, of course, Star Wars Sequel Trilogy.
4) The fourth films are very often really a new beginning, resurrection, rebirth, reboot - call it what you want. Sometimes these films try to continue the triquels, sometimes they try to cancel them. Sometimes they come out good, sometimes they don't. Unlike the mostly bad triquels, the fourths can be called "dubious". Examples: Alien: Resurrection, Terminator: Salvation, Robocop reboot, Jurassic World, Indiana Jones and the Kingdom of the Crystal Skull, Tremors 4; possibly Matrix 4.
5) Fifths of the films are free fall territory. You can expect anything. Good things, bad things. New ideas, old ideas. Continuation or reboot. Quality also defies calculation. Examples: Prometheus, Terminator: Genisys, Jurassic Word 2, Tremors 5.
