I really liked Mykonos, and the single people on the cruise did as well. Some argue that it is "too gay" or "too touristy" and that other Greek Islands are better. Still, it's quite beautiful - not just the houses. :o)
Mykonos, Greece is supposed to be really nice.
So is:
Amsterdam, the Netherlands
The Hague, ^ ^
Santorini, Greece
NOT the Caribbean--have heard they are VERY homophobic.