You can't go wrong with Manny. Not only he was the greatest pound-per-pound boxer but he's doing wonders for his country. That makes him also the greatest out of the ring. May he be in our hearts forever!
My favorite boxer of all time is "Muhammad Ali" and if you are asking about the present then it is "Beibut Shumenov"
My favourite active boxer is 'Juan Manuel Marquez'. He has 7 losses on his record and you could argue 5 of them shouldn't be there! Excellent boxer still, despite being in his 40s!
Oh, how I wish I were able to give you a like for that. I personally like Pacman. I want to like Mayweather, I really do, but I just can't get past the ego. I've been to his gym a couple of times to talk with his uncle Jeff (who is cool), but Money is just too over the top for me.