On that poll I'd say Ariel Winter is the deepest
In terms of best shape and bellybutton overall - it still has to be Victoria Justice. It's just the perfect circle and detail inside!
Best tummy and bellybutton combined, Bella, and dare I say it Paris Hilton have to be up there.
I'll throw an honorable mention to Nikki Soohoo. Most of you probably won't agree, since she isn't nearly as famous as the other girls, and that she's too youthful and cute looking to be sexy, so any attempts of her trying to be sexy comes across as awkward. But man, her innie looks like if you tried to poke it, your entire finger would disappear. And the rest of her belly is nice, too.