Sure they are well compensated, no argument there. Though in regards to "compensating differential", I don't think NFL players are highly compensated because it's an undesirable, unpleasant job, or because of the health risks. They're highly compensated because of their talents. There are a lot of amateur leagues and conferences were football players are paid nothing.
I guess what I'm getting at is what's my moral responsibility when I have people give (shorten) their lives for my entertainment, for sport?
I think that because it's "for sport", (and "entertainment"), that this is a significant difference than asking someone to give/shorten their life for country (military service), or employment in a job that (hopefully) contributes basic needs (food, shelter, clothing, warmth, health) to society (e.g. dangerous jobs: the coal miner who will get black lung, the lumberjack, the farmer, sanitation worker ).
(These are some of the most dangerous jobs, but not the most highly compensated.)