What are some alternatives?
When comparing Simkl and Rotten Tomatoes, you can also consider the following products
IMDb - Internet Movie Database
Letterboxd - Letterboxd is a social site for sharing your taste in film, now in public beta.
Metacritic - Metacritic aggregates music, game, tv, and movie reviews from the leading critics. Only Metacritic.com uses METASCORES, which let you know at a glance how each item was reviewed.
Trakt.tv - Automatically track TV shows & movies you're watching.
Filmsomniac - Filmsomniac.com | TV Tracker | Movie Tracker
Criticker - The TCI is a measure of the similarity between two people's taste in films.