Ray J has one of the worst singing voices. It has a waver and a whine to it that grates the ears. That said "One Wish", hell the entire Raydiation album, is a smash and only Ray J could do that.
Ray J is a perfect example of using swagger, connections, and confidence to make people accept your lack of talent. He sang his ass off on that track. Then he did everything that needed to be done in that video. The album is well produced, the songs are fun. I will say the album occasionally sounds like the songs that were rejected by other artists and R&B groups.
Would I love to hear the song(s) in the mouth of a Mario or Usher or anyone else? Sure. Would I still prefer Ray J? Absolutely. "Melody" and some others stay right in his range and never require him to hit notes outside of it and they are the better songs.
"What I Need", "Lets Play House", and "Melody" deserve more recognition. I'm saying that about the whole album on my re-listen. Mya and Brandy both feature on the album. Ray J has something that works and he knows how to work it.