I've got to agree with Gaz. Until you've dived with a selection of DM's, it is hard to say who is the *best*. Even after you've been diving with a bunch of different DM's, it's hard to say who is the best. They are each different in their own special ways. And so even after you've been diving with a bunch of them, all you think you are sure of is who might have been the better diver, the better guide, the better shepherd, but in the end it often comes down to who fit you the best. What is each person's personal skill level to be making these calls?
Now having said all of that . . .
As for what else I'll totally support Gaz on, is, of all of the DM's that I've been diving with in a number of places in this world, not just Belize, Andy Palacio, was one of the very best so far.