I vote no one. To me, Pamela Anderson is the standard cultural reference for the blonde beach bimbo celebrity archetype. Yes, that means she has the big chest but that’s just because that is one aspect of the archetype. Dolly Parton contrastingly is the standard cultural reference for big tits. Full stop.
If someone does a Dolly joke, it’s a boobs joke. If someone does a Pamela joke it could be about sex tapes or bimbos or blondes or whatever.
It was definitely Jane Russell in the late 40s and early 50s. You’d be surprised by the number of blatant big boob jokes about her Bob Hope was able to get away with in that era.
Nope, it’s STILL Dolly Parton.
About half way between Los Angeles & San Diego in SoCal is the San Onofre Nuclear Power Plant. My husband & I still refer to it as "the flashing Dolly Partons.
There are many, many celebrities with nice racks, and I’m sure there are a few who’d make Dolly Parton look like Audrey Hepburn. But with Pam Anderson being past her prime, Anna Nicole Smith being dead and Jenny McCarthy being a crusading mom, there’s no *iconic *set of boobies out there that everyone can rally around.
Christina Hendricks? Supporting role in a cable show. Jennifer Love Hewitt? Not even in the same league. Kim Kardashian? Booty, not boobies.
Besides that, these days we’re more occupied with whether they’re real or fake than to stand back and admire them.
In Sweden there is a road sign that says Fart-hinder Which as near as I can tell means Dolly Parton is lying in the road ahead. 
True. Someone mentioned Kim Kardashian, and her name/ass itself does seem to be a punchline.
