I am trying to know which is for you:

1) The best and the beautiful beach in Europe.
2) The country with the best beaches in Europe.

The beaches of Formentera, Spain. Absolutely stunning, and not too many tourists (especially surprising when you consider it's right next to Ibiza)

Southern Baltic Sea has the best beaches - from German coast to Estonia. It's all sand, no pebbles or stones.

I would recommend spain. Baltic sea is gordeus, but a bit cold. My favourite city is Barcelona, even if the beach is not the most beautiful in the whole Europe you can reach some very nice ones in 20 minutes taking a train (f.ex. playa Castelldefels) enjoing at the same time the advantages of a big city.

The Dalmation Coast in Croatia! Beautiful beaches, and the water is such a pretty turqoise. The villages along the coast have some really good restaurants and night clubs. And, the Fortress of Dubrovnik is not that far away, perfect for a day trip.

Also some of the Grecian Islands have fantastic beaches and once you get there you can stay and eat for pretty cheap. Rhodes, Santorini and Mykonos are popular favorites, but you might want to check out Ios, Naxos and Kos for some of the best hidden beaches that are not flooded with tourists.

Oh and one more to mention and I have to admit this is one of my favorite beaches in Europe. Omaha beach! Its not really about WWII, although the rolling green hills that melt into the beach are filled with Nazi bunkers that you can go explore. But, its the long, wide sandy beach filled with families picnicking under large umbrellas and kid's making huge sandcastles nearby, and dogs catching frisbee's and running in the shallow foamy surf. It's such a great place, and lots of good seafood restaurants.