If he'd played for Dallas as long as Emmitt did, he'd have that record. If Sanders gave a damn, he'd have that record.
No doubt Emmitt was a great RB, a top 10 of all time, but when first contact is beyond your own los as much as he got, you get longevity and lots of yards. That's not taking anything away form him but there are quite a few RB's that would have that record given the opportunity and OL and O he had.
I have only seen one back in my years of watching this game that had the kind of connection with his OL that Emmitt had with his, OJ Simpson in BUF. And that is a talent as well as that doesn't come easily.