My favourite beaches with good resorts attached (and I LOVE a good beach) in no particular order

Amanpulo (just got back from another immaculate stay)
Aman Sveti Stefan (Queens beach and to worry about the corseness of the sand misses the beauty of this beach i think - it is stunning partly because of the more rocky nature and the clean, gorgeous water and scenery)
Lizard Island
All of the Maldivean Islands i've been to
Anguilla (Shoal Bay East i think was my favourite on the Island but no where remotely high end to stay on that beach - maybe Ku?)
Mauritius - beach of the Residence and Ilot Maganie i agree is better than the beach at Le Saint Geran
Mnemba Island
Several in St Vincent and Grenadines area - Petit St Vincent, Palm Island
Amanpuri