In my opinion I think that
-> If you use "In my opinion", you can omit "I think that" or vice versa
These films are what we call action movies, and from their names we can see that strong scenes, like car chase, explosions, and more are important parts of the movie's plot, and that it is somewhat necessary.
-> You can split the whole sentence into 2 shorter ones. I feel a little bit confused when reading this.
; as an important factor of the story.
-> which are such important factors
the film industry is making all kinds of movies that have their audience
-> with a view to attracting millions of viewers
hadn't changed one bit in the history of movie making
-> hasn't changed much ...
the explosions that where created in old movies differ greatly that the one created in new ones
-> that were created... differ greatly from those in modern films.
I hope these help.