It looks like the average 4-year degree is worth less than the average NFL earnings - the two figures I found Googling were $2.1M for lifetime earnings from a 4-year degree, and $4M for career earnings for an NFL player.

On the other hand, engineering degrees tended to hover around $4M for average lifetime earnings, and some engineering fields (petroleum engineer, SV software engineer) averaged ~$6.5M in lifetime earnings.