Joe Cal trained like a beast. Roy Jones used to train all year round. Hopkins does train all year round. Hatton used to train like a machine. Elite level boxers have to train hard, or they won't survive.
Amir Khan trains like a madman apparently. Froch is pretty much always in condition and trains hard. Loads of top guys do, they just don't have a camera following their every move like Floyd. Most also fight alot more than him.
Hanging out at boxing gyms in Vegas is interesting because you see how a lot of pros train. Some are lazy and talented, others are HARD WORKING and not talented. Floyd is both. None of his exercises are super super elite - those standing sit ups he does aren't that hard, just cool. There are a lot of guys who look even better than him hitting the bags ... He trains hard and he has loads of talent. Hagler trained just as hard. It's just some don't have the natural abilities to be elite. Other guys like Derrick Harmon mostly train to lose weight, they aren't insanely dedicated trainers, but have a decent amount of talent. Cotto and Morales kind of look like lazy trainers but they have the intangibles that make them excellent fighters. Oscar was mostly talent attached to a garbage work ethic.
Constantly being in shape is what the best boxers possess as a real skill. Floyd is one of them, Hopkins, Sugar Ray Robinson, Joe Louis, Marciano etc. Now look at guys who only work at camp and blow up between fights....and how fast they decline....say like two guys as of late that are good examples, JMLopez, Pavlik. Staying in shape at all times is a real skill and proven dedication, Floyd possesses this but so do many other elite fighters of now and all time.
Wilfred Benitez, Roberto Duran, Corrie Sanders, James Toney, Riddick Bowe, and especially Kirk Johnson. Really, there's no way to know. Mayweather trains really hard. So does Bradley, Hopkins, Pacquiao, the Klitschkos, and numerous others both present and past.
I forget the name of the boxer but i remember reading about his training. His trainer said he lived about 8 miles from the gym and every morning he would run to the gym, train then after training he would run back home. I cant think of the name at the moment. Anyone want to jump in??