You know what? You’re right. He should. He just isn’t as iconic as Bo and Herschel were in CFB but his production takes a backseat to no one.
Bo and Herschel were at the end of what I consider to be the Golden Era of college football, which is basically the 60s through the mid-80s. The sport was a lot more "rah-rah" and less cynical in those times. Players tended to be built up by the media, rather than torn down.
The increased exposure of college football due to the end of the NCAA TV monopoly, combined with the advent of sports news television and eventually the 24-hour news cycle applied to sports, resulted in more widespread information about more players, and also decreased the media's tendency to hype one player in favor of a multitude of others. It certainly didn't END that practice, look no further than guys like Tim Tebow or Reggie Bush, but there became less of a common narrative in sports media, and a bigger free-for-all.
I think if Ricky Williams had done his thing in the 70s or 80s, he would have been considered more iconic. Earl Campbell's stats aren't as impressive as Ricky Williams', but I'd say he's considered much more iconic in the manner you're attributing to Bo and Herschel.
Just a few thoughts, all those guys were fun as heck to watch play the game.