Dilfer and Johnson are in the minority here...and look at those defenses that they played with. Look at the studs even in the last 20 years that have won SBs...Aikman, Favre, Elway, Warner, Brady, Manning(s), Rodgers, Brees, Young, Roethlisberger. All of these guys are HOFers or at the least borderline HOFers.
Hostetler, Dilfer, Johnson are on a very short list of non-elite QBs who have won SBs. If I'm a betting man, I like my chances with a stud rather than a dud. Even Rypien's SB season was spectacular, although his success was short-lived (think he was a 2 time pro bowler).
It is very much a team sport, one in which you need a great leader directing the team.