I don't know anything about the number of game winning shots, so you may be right about that, but neither of those guys can really take over games like Kobe or D. Wade can. Making clutch shots is one thing, but single-handedly changing the way the other team plays is something else entirely (and Kobe had some of that even early in his career). If teams had to pay even less attention to Howard than they do, he would look that much better, and I think that is why Shaq really succeeded when he had one of those guys around him.
But whatever the case, I personally think a lot of credit for the Magic's success goes to. . .the coaching
People always like to criticize Van Gundy, but the guy knows how to create match-up problems, and has made some great play calls at prime times.