In an all out battle of magic which one do you think would come out on top? Merlin versus Gandalf versus Dumbledore, battle of the old long bearded wizards begins.
Gandalf is the coolest out of all of them, but I have yet to see many of his powers. (I like his fireworks.) If I had to pick, I would choose Dumbledore. I've seen his powers, and they're pretty cool. Oh, and I think Merlin was actually an evil wizard, contrary to the famous tale, wasn't he?
Umm... I think that Dumbledore is more powerful magically than Gandalf, but Dumbledore's dead, so that automatically makes him less cool xP. Merlin just isn't cool. So I'm going to have to say Gandalf. He's got pretty impressive magic powers and intelligence, as well as being able to bash your skull in with his staff if magic doesn't work.