The Game -- Serena Williams is the Next Rap Superstar

The Game thinks Serena Williams is an AMAZING rapper and if she decides to drop an album, it's sure to sell big ... this according to the man himself.

Game tells TMZ ... after he heard Serena's rap for the first time, he knew that she definitely had "raw skills" and was a "really talented artist."

Game says he wasn't that surprised ... considering the tennis champ's Compton roots. He tells us "You shouldn’t expect her to come with anything less than the official rap bars," then added "I can see her doing big things."

Kind of like winning 2 Olympic gold medals, 3 US opens and 4 Wimbledon championships.