Juanma, Gamboa, Rafa, Donaire, Hasagawa, Montiel, Vic ...theres too many. I would say Donaire is the most interesting to watch for me, but for excitement I'd say Juanma.
I'll go out on a limb while James Kirkland has been incarcerated at the pleasure of the US taxpayer and say Victor Ortiz for me.
Pacquiao. Hands down. The perfect combination of popularity and excitement unlike Floyd, who is immensely popular, but only occasionally exciting.