It all depends on one's criteria for choosing their list. Montana made his "name" as a pro, not as a college player where he wasn't all that "special." For me, based on his play while at ND, he wouldn't even make my top 20. Heck, he have a hard time cracking the top 5 best players on ND's '77 NC team and '78 was a pretty unremarkable year (8-3) save his performance versus Houston.
As a relative contemporary of Montana at ND (as a matter of fact I knew his first wife), I was pretty startled that he became the player he was. The best way I could say it was he was a bit disengaged at times and downright lazy most of the time at ND. But we all find our special niche at different times in our lives and Montana found it after ND.