I saw a retrospective show of his in Paris last summer, and knowing the basics of his work... The decisive moment, blah, blah, blah... I must say that his work was very well seen. It impressed me a great deal.
I think part of his draw is that he was one of the first "rock stars" of photography... A big name in a field that didn't have that many big names yet... This is just my opinion, but one factor I believe...
Rather than show people what they never saw, he had an ability to show people what they saw everyday, but in a new way. Many images had a sense of joy in them that made you feel good to look at them... (I'm thinking of the picnic on the river bank and the little boy with the bottles of wine... to name a few)
Just an opinion,