In order to be believable, Getting the right actors in my opinion is one of the most important aspects to a well made movie, show, etc.

TV shows that I see on Netflix are mostly boring, cringe worthy, and almost seem drawn out. I saw this happening when I saw a couple of episodes of Santa Clarita Diet. This show has a great plot and could have been done well, if it weren't for the actors that make it seem as if they are role-playing, and not actually representing a character. The punchlines are sometimes over exaggerated by the actors and sometimes the actors are just unnecessarily loud.
I feel the actors simply ruined a great idea for a movie, shame. In the case of Zathura: A Space Adventure, the opposite seems to happen. The movie is clearly trying to coat tail from Jumanji's success and uses the same idea of a board game that comes to life. Usually im not fond for unoriginality, but, the actors in Zathura made me enjoy it even more than Jumanji. My love for space might have created a bias towards it, but I believe the actors really sold that they were outer space and actually in a disaster of a situation.
In the Netflix series, Stranger Things, I believed that the kid actors were not believable. A controversial opinion, but it is still my opinion.