First of all, it's too early to tell, he's had only 26 NFL games.
Emmitt had a 4.2 ypc, only 4.6 or better 3 times in 15 seasons. Even in his best year, 1995, he was at 4.7.
Zeke is currently at 4.6 for his short career, even running behind this line Sunday he had a 4.6. Only 15 carries, if he'd had more I submit the defense would have worn down a bit and he would have had over 100 with "only" 22 carries. Any running back not named Barry Sanders needs holes to run through.
You don't judge somebody as a franchise running back year by year, you take his total body of work.
As I said it's too early to tell whether he is, or is not, a franchise running back....