This is more of an opinion question, it all depends on what you enjoy watching. Riverdale is more of a teen drama, mystery and crime type of show. While Stranger Things is more of a Horror fiction, supernatural thriller type of show. It all depends on what you like and enjoy the best. But if I had to pick, I would pick Stranger Things personality because the show dosent get lost in the middle of the series like Riverdale. But again, this is all a opinion question.