Systems Analyst – 32
Chemist – 31
Electrical Engineer – 30
Engineer – 29
Programmer – 29
Accountant – 28
Executive – 28
Reporter – 28
Teacher – 28
Copywriter – 27
Investment Analyst – 27
Librarian – 27
Electronics technician – 26
Salesperson – 25
Secretary – 24
Dispatcher – 23
Drafter – 23
Electrician – 23
Nurse – 23
Bank teller – 22
Cashier – 21
Offensive tackle – 26
Center – 25
Quarterback – 24 (Most teams want at least 21 for a quarterback.)
Guard – 23
Tight end – 22
Safety – 19
Linebacker – 19
Cornerback – 18
Wide receiver – 17
Fullback – 17
Halfback – 16
It's also worth mentioning that the O-line often has the largest cognitive overhead during a game, as they have to memorize and execute complex blocking schemes, work together to enact subtle feints, read/pick up blitzes/additional rushers, all while fending off an equally large and quick defensive tackle. The center can also override the quarterback's play calls (under certain offenses) if he notices a defensive shift or audible.
It's definitely possible to win a Super Bowl without a star quarterback, wide receiver or running back, but nigh upon impossible to win it with a weak front line.
I know a few people who've gone on to succesful careers after playing rugby at a high level - but they did one then the other.
Although, it's not that hard to believe. Many many offensive linemen come from top-tier schools (like Fleener, who went to Stanford) and it's becoming more common for QB's to do this as well (like Andrew Luck, who went to, well... Stanford).
Although, it's interesting that in the average scores, the "skill" positions (WR, FB, HB, etc.) all have lower averages than the non-skill positions.