Wasn't handchecking allowed during Jordan's days? Handchecking makes a big difference, because with it you can sense earlier where the person with the ball will go next. If Jordan played without handchecking, he might've been even more dominant if that's even possible.
I agree that LeBron is a more impressive physical specimen than Jordan. Tool for tool, LeBron has more potential than Jordan and is already probably a "better" basketball player.
But we're talking about greatest ever, not most potential, and that means getting it done. That means championships, because the objective of basketball isn't about scoring points or grabbing rebounds or making passes...it's about winning. And the greatest ever should be able to do that. Until LeBron wins a championships, I don't care how much potential he has or how good he looks -- he doesn't have claim to the greatest ever title.
Say what you will, that's how the world works.
Nobody cares if you're the smartest or most hardworking guy. I'm sure there are more talented guys than Mark Zuckerberg or Steve Jobs, but those two guys got it done. Sure, sometimes it takes a bit of luck and it's about the stars aligning, but it's still about achievement not about potential.