Rotten tomatoes suck at giving reviews and would never go by whatever they say and they wouldn't even know how to review their own site if they had to. Yea Rhianna was in it but that didn't break or make the movie imo, some may feel otherwise but in the end it's an opinion on anyone's view...You actually liked Battleship? That movie got terrible reviews. Rihanna was in it? And the whole thing just advertised a board game. Rotten Tomatoes gave it 34%.
(Going a bit off topic here I guess )