Canelo has dramatically improved. Man, I didn't realize he was so quick. Really nice jab and follows it well. That makes things very difficult for your opponent. EDIT: I don't think Mayweather would want any part of Alvarez now. I'm not saying Floyd would necessarily lose, but it wouldn't be like it was the first time around.
When I boxed, I was so much taller than my opponents and my manager focused on my jab. That and a strong right cross can be a punishing combination. If you can just beat your opponent with the jab, it sets up everything.
As far as the poll goes, I'd have to go with Ali. There's a guy who, by the end of his career, I think may be on that list (and very possibly high up on the list). His name is Vasyl Lomachenko and he looks to me to be about the best boxer I've ever seen. This guy comes at you from so many angles with so many different punches that getting a read on him seems almost impossible. There just don't seem to be any patterns. It's like going up against a pitcher that throws 6 different pitches for strikes; there's no way to tell what's coming next. Keep an eye on this guy. He's only had a few fights, but, man, is he ever exceptional.