My two cents worth (or less):
Who was the most celibrated sports icon in Miami before Marino? Don Shula.
I love Shula. One of the greatest football coaches of all-time. But how many young fans remember him coaching the fins during the glory days?
My point is time makes great sportsmen into legends, but in time, these legends will fade by the very nature of sports being a "what have you done for me lately" business. If--and that is the operative word here--Wade becomes a Tom Brady like figure in Miami and leads the Heat to a few more championships, I think he will surpass even Marino simply because the new generation of Miami fans will have grown up with him and will relate to him more. But, isn't it nice to have the Shulas, Marinos, and Wades to represent Miami sports?
Something to ponder: In 100 years, assuming the world hasn't blown itself up or south Florida isn't underwater, how many kids will know who Shula, Marino, or Wade is, aside from the fact they ride on a highway named after him everyday on the schoolbus?