No he's not the greatest vocalist, neither was Michael Cooper of Con Funk Shun. Now tell me when you listen to "Love Train" is that not a great vocal performance. He realizes he's not a great vocalist which is why stays within in his range, short burst of falsetto's nothing on the level of Phil Bailey(of Earth Wind & Fire), Low levels of Tenor that doesn't rise above his in studio performance, this is why for the most part it translate to his live performance. Listen to his Jimmy Fallon performance of Bad Religion and then listen to the album version.
Dont ever in your long legged life compare con funk shun to Frank Ocean. I dont want you to do that anymore. Frank ocean is a horrible vocalist. Lets just get that out the way. Even on his CD some of his vocals sound like He has no vocal range and his singing style is channeled purely from whining. I bet hes the easiest artist to sing covers for on youtube.