What is the best video game rating

If you are referring to ESRB ratings, it depends on what you want out of a game.

The ratings are dependent on the content of the game and how appropriate they are deemed towards a certain age-group, but these ratings do not make a game better than other with a different rating.

Games that are rated as Mature Only might include profanity, nudity or extreme violence, but they might be, regardless, very good games.

Simultaneously, games rated for all ages tend to be simple, not very involved and lackluster in story, but this doesn't mean all "All Ages" games are bad.