Up until late 2008, I would've said Gwen, but then this came along:
So, I voted for Rihanna. I haven't heard an artist with very similar vocals yet. Now, if we were going by vocal talent, I would definitely be voting for Gwen, but this isn't talent, this is uniqueness in vocals.
I remember people thought this was Rihanna, but that wasn't her.
That's because Akon says "I said Rihanna"
And also, "Rihanna" sings "I got a call from my friend saying, RiRi"
Rihanna should have recorded this song. Such a shame, it could have been (And still can be) a worldwide smash. I think Rihanna should record it for Loud re-release.
Gwen Stefani of course. I like Rihanna too, but Gwen is a lot more versatile in her voice. She can do pretty much everything, every kind of song/genre. Kind of like Fergie.