Because your "main point" was backed up by literally nothing.
You: Barry Sanders is better than Emmitt Smith
Me: Why?
You: Emmitt played for 5 more years, with better players, and "only" rushed for 3,000 more yards.
Me: .....................................
You've got your "all-around back" argument. That's the only argument I've seen from you.
But you're right, I didn't quite flesh out my argument. So here we go.
Barry's a better runner. Over his career, he averaged 5.0/carry. Smith averaged 4.2/carry. Barry set the record for most consecutive games with 100+ rushing yards with 14 games in one season with over 100.
Smith fumbled twice as much as Sanders did. Surely this is due to the bruising style that Smith had, you say? Sanders had an equal if not greater chance to fumble by running through/in between tacklers via his running style.
Emmitt Smith's line was dominant in run blocking. Sanders line wasn't full of slouches, but it was nowhere close to the protection Smith had over his years in Dallas. This should allow Smith to run for more yards than Sanders (I write this only because you dismiss the fact that Smith had a better line as if I was saying he had a better defense).
"Well, Smith is the better all-around back."
Not exactly true. While Sanders wasn't as good at blocking as Smith was, he was at least as good receiving-wise. Sanders averaged 8.3 yards a catch compared to Smith's 6.3 yards a catch. Smith got only one more touchdown catch than Sanders and only 303 more receiving yards on 163 more catches.
So there is my argument. Full.
Barry Sanders running skills > Emmit Smith running skills
Barry Sanders catching skills > Emmitt Smith catching skills
Emmitt Smith blocking skills > Barry Sanders blocking skills
Barry Sanders is the better running back.