<<If you were playing against a bunch of guys 2-3" shorter and 40-50lb. lighter, size alone would not allow you to dominate.>>
Wrong. I do it to my friends all the time. They pass me the ball near the basket, and I simply back them up until I feel like shooting. Remember, Shaq does this to other centers, not other guards and fowards...the little guys would pick his pocket, or he'd shoot over them(if he could actually shoot).
<<And I'd be willing to make that bet. I'll find you some 300lb. guys, or, I can show you that they're NOT in the NBA, and Shaq is among the few guys that are. >>
It isn't just Shaq's SIZE, it's his BUILD. Yes, there are plenty of fat 300 lb guys around,(very few that are 7'1" though), but NOBODY in the NBA is Shaq's overall size AND build. No, you couldn't bulk Garnett or Robinson up and have them hang with Shaq because they're not built that way, their frames wouldn't support that weight.
On the other hand, if you took someone else with Shaq's build and gave them Garnett's or Robinson's talent and skills, you'd have the best player in the history of the sport, someone who'd average 50pts a game easily.
Kind of like Wilt Chamberlain, but a bit bigger.