as for me... some vocal acts mentioned here are plain. I don't see vocal examples there.
Since when has pre-record become a weak point?.. Well, I won't tell everybody uses it. At least, Rihanna tries to sing along and doesn't just shake ass with her mouth shut, while the studio version of the song is playing on the background... Then, wait, are you talking about her singing quick songs badly?.. everybody might seem a bit off key on this type of songs sometimes, because these songs are more difficult to perform. It's just how you choose to hear
Also, I think all the YouTube compilations don't show her at her best.
They became better for now, though.