The A380, because the other two are Boeing .....
Seriously though, out of those three, I've only been on the B747, so as far as comfort goes, I'll have to say the 747, however, I do find it too cramped with the 3-4-3 seating and will opt for the 2-4-2 seating of an A330/340 or 2-3-2 of a B767 over the B747 anyday.
As far as styling goes, I'll have to say the B747 again, the bump just gives it that little something extra. Second place would go to the A380 just for that fact that it is a true double decker and although someone awkward to look at, Airbus did a good job on it. The B777 is just another generic twin jet out there and the length of the 777-300 makes it look something I built out of Lego. God awful looking plane and I would even place it as one of the blandest airliners ever developed.