I'm not really a beach person as I often end up like sandpaper in no time. Nevertheless I have been priviledged to visit a lot of the most spectacular beaches around the world.
I assess the beaches in the southern hemisphere - particularly far out in the Indian and Pacific Oceans, to be the best - probably because they are so far from civilisation. But there are a lots of fantastic beaches many other places.
The good news is that it's still fairly easy to find your own secluded beach if you just get off the beaten track. Take a local bus to the non-tourist side of the island you're on and walk a while along the water - if any people at all, you're likely only to stumble on a friendly old fisherman.
I have written a comment at the first picture from every new location - when no comment the location is the same as the previous picture.