I played football for 9 years (1 in college). I made my best friends playing football, gained confidence, learned countless life lessons...but I still wouldn't let my future children play the game because of the risk of brain injury. A few weeks ago, I had a conversation with a former teammate where we wondered if there have been long-term effects on our brains. And we played at nowhere near the level of the athletes here.
I'm convinced we're going to see football go the way of boxing. Boxing still exists, but it doesn't have nearly the appeal that it did 40-50 years ago, when a quarter of the planet watched The Rumble in the Jungle. [0] Boxing (competitive boxing, not workout classes) isn't a sport that upper-middle class kids get involved in. Youth football is headed in the same direction; participation rates are down as parents don't let their kids play (and other sports increase in popularity).
Every activity we choose to engage in comes with some degree of risk. The ethical issue here is twofold:
1) Do we adequately understand the risks, and are the people playing the game (children) equipped to make the decision of whether or not to play?
2) As a society, what degree of risk are we willing to tolerate? How many suicides is too many? [1]
[0] https://en.wikipedia.org/wiki/The_Rumble_in_the_Jungle
[1] I have mixed feelings about Malcolm Gladwell, but his podcast on the ethics of football (especially as it relates to higher education institutions, whose missions run counter to the idea of bashing one's brain in) was thought-provoking: http://revisionisthistory.com/episodes/22-burden-of-proof