Italy, Croatia and Slovenia?
The classic big 5 (in no particular order) are Egypt, Bulgaria, Greece, Turkey and Spain (with Croatia gaining in recent years) Italy is a bit behind (maybe because it's more expensive). I was in Sardinia a couple of years ago and loved it, but local transport was either really inconvenient or very expensive.
Cyprus and Portugal and Malta are all also popular. Tunisia was very popular before the terror attacks and Morocco is maybe creaping into the picture) as are maybe Albania and Georgia.
No one goes to Slovenia for beaches... how much coastline do they have, 20 meters?