Rihanna is far from being a great vocalist, but she is by no means the worst vocalist that ever touched a mic. Sam likes to exaggerate the "mediocrity" of Rihanna's vocals. There are worse singers in the industry. Besides, even the likes of GaGa aren't known for their vocal skills. As for Ora, she can sing better than Rihanna, but it's not as if the difference is much. Thatgrapejuice are too biased and can exaggerate stuff.