Best sand?
Best sandy (not rocky or seaweedy) bottom?
Best snorkelling?
Best natural beauty?
Best man-made beauty?
Best beauty what belongs in a bikini?
Best water temperature?
Best waves?
Best snack bar?
Best parking?
Best (fill in the blank)?
Pick any beach in Anguilla and you’ve got your answer to all of the above (except snack bar - there aren’t many).
That being said, the best beach for people watching is Haulover Beach just north of Miami. The nude section, not the prude section (which has no one on it to watch, not surprisingly).
Best unnatural beauty in a bikini: Rio
Best people watching: Jones Beach, NY or Venice Beach, CA
My favorite: Coal Oil Point (sic), just west of Isla Vista, California. Nice dunes, no one around. (At least 30 years ago – don’t want to know if that’s changed, thanks in advance.)
Best sand?
Best sandy (not rocky or seaweedy) bottom?
Best natural beauty?
Best waves?
Best parking?
Best sunset?
All on the Long Beach peninsula on the Washington coast. The sand is half a mile wide, over 28 miles long, you can park and drive on the beach and sunsets that go on forever.
St Maarten’s Friar’s Bay beach and Pinnel Island beach would be tied.
And hottest goddam beach on the planet: Siloso Beach, Singapore.
Playa Tecolote http://www.baja-web.com/la-paz/index.html
North of La Paz , Baja Sur , Mexico
To answer my own questions, I’m going to disqualify that little beach in Nassau. Except for snorkelling. Damn fine snorkelling. And great water temperature, even in December.
Best sand? Old Silver, on Cape Cod
Best sandy (not rocky or seaweedy) bottom? Same answer
Best snorkelling? Other than Nassau, State Beach on Martha’s Vineyard. I saw crabs mating!
Best natural beauty? Gay Head. Didn’t even have to think about that one.
Best man-made beauty? Gay Head
Best rock stacking? Gay Head
Best beauty what belongs in a bikini? Gay Head
Best water temperature? Old Silver. It’s got that Gulf Stream thing going on, making it like bathwater.
Best waves? Second Beach, Newport RI.
Best snack bar? Naraganssett Beach. RI.
Best parking? Anywhere on Amelia Island, FL. It’s free, unpaved, and uncrowded.
Hey, I live on the East coast. No fair.
But I have to say it’s a tie.
Eastville Beach on Martha’s Vineyard. One sunset made me order my GF to “Stop the car!” Blue sky, pink clouds, violet water. Awesome.
Front Beach in Rockport, MA. To my right, pinky purply sky. To my left, sailboats in a field of velvety blackness. In front of me, Venus.
I’m partial to Trunk Bay and a couple of others on St. John, USVI for nice sand and water and snorkeling.
The sand on the Redneck Riviera (the FLA part, anyway) is the whitest I’ve ever seen.
What’s the Redneck Riviera? St. John river? I remember the sands of Cumberland Island being really white. That place is easily my runner-up for best natural beauty.
Redneck Riviera runs from Pensacola to Destin (maybe even a little further east). Yes, the sand is beautiful. I used to visit Navarre Beach a bunch (and went to the clothing optional part near Eglin quite a bit. The Air Force was OK with it as long as you didn’t go near the radar installations).
Ocean City Maryland
Ocean City Maryland
Vieques Puerto Rico. Snorkeling over Unexploded ordinance is cool. 
Vieques Puerto Rico. You can see St. Thomas from there and it has a lot of need twists and turns.
Puerto Rico
Puerto Rico
Ocean City Maryland and Southern California
Vieques Puerto Rico, Sun Bay campground serves Pina Coladas and other frozen drinks.
Sun Bay in Vieques again, lots of parking, but you have to be careful about getting robbed by the locals, there’s a bit of a pirate culture around there.
Mosquito Bay in Vieques.
Best sand, sandy bottom, snorkelling, natural beauty, water temperature all to go Matamanoa, Fiji. Tiny little island which was just amazingly beautiful with reefs right off the beach absolutely chock full of tropical fish. I’m sure other islands in Fiji are comparable, but it’d be hard to do much better.
The beach around Basin Lake, Fraser Island, Australia. Absolutely stunning.
A photo that always makes me nostalgic.
(and the coastline wasn’t bad either)
Lake Michigan has some world class beaches. No really. At least as far as sand and sunsets go. And sometimes bikini beauty.
For almost all of those questions, it’s Ka’anapali Beach on Maui, it’s as great as the accolades it receives. The best snorkeling I’ve done off a beach was at a tiny little beach in South Maui whose name I’ve forgotten. The best natural beauty would be Canon Beach in Oregon.
I’m not as much of a beach connoisseur as you are, so I don’t have answers for most of your questions. I’ll just say that the beach I liked the best was in North Carolina in the Outter Banks.
How come? I love the beaches in the Bahamas.
With a filename like that, I was pretty underwhelmed by the photo.
In the US, I’ve been to beaches in NC, SC, FL, MA, WA, and CA. NC is the best IME.