Wow are your stats ever off. Holy crap.
First, a quick google of "Minimum NFL Salary" shows that the minimum is 450K, not 750K as you claim in your post.
Second - that's NOT for players that will never step foot on the field. THOSE players, known as "Practice Squad Players" can have their salary found on the second result of the same search: $7600 per week. And I can only assume that they only get paid for 16 weeks, so that works out to $121.6K per season.
Third: the top 3 NFL salaries right now?
Jimmy Garoppolo, San Francisco 49ers.
2018 Cap Hit: $37 Million.
Matthew Stafford, Detroit Lions.
2018 Cap Hit: $26.5 Million.
Derek Carr, Oakland Raiders.
2018 Cap Hit: $25.0 Million.
Sure, those are all between 8M and 50M as you claim, but you're implying 50M is possible. The top player makes 37M, and then 2nd and 3rd are only at HALF of your maximum...
Then tennis... oh tennis. Holy crap. I didn't know a thing about the NFL before writing this post and yet I knew you were full of it by how far off you were on tennis. A tennis player does not make anywhere close to 50M for winning the US Open. Where in the world are you getting that figure from?
Roger Federer, the winningest player of all time, has career lifetime earnings of $120M. That's with 99 tournament victories, including 20 slam victories.
Djokovic, the highest prize-money earner (due to recent tournaments paying DRASTICALLY more than prior years) has lifetime earnings of $125M with 72 tournament victories including 14 slams.
The most recent slam, the 2018 US Open, paid a grand prize of $3.8M.
Your $50M figure? Well, that's pretty much the total prize money ($53M) paid by the US Open to ALL Competitors, INCLUDING THE WOMEN. And with equal prizes (somehow... when the men have to play 5 sets and the women only 3, talk about equality...) the men share a 26.5M prize money among 128 entrants. Players earn $54K for qualifying (i.e. playing in the main draw and losing in the first round). While that may still seem like a lot of money for losing, between having to pay their coaches, travel, accommodations, etc... a first round exit is definitely not a pay day.
And these numbers have gone up significantly!
Only 8 years ago, at the 2010 Wimbledon Championships, the victor received 1M pounds (about $1.3M USD, however at the time it may have been closer to 1.5M USD). A first round loss paid only 11250 pounds. At that time, a first round loss likely meant the tournament lost you money. And tennis has been around for over a century and it's only seeing the increase in the last 8 years or so. League of Legends has only been around for 8 years.
Onwards to the rest of your discussion:
Most professional athletes make far more off the field than on the field. Federer is paid far more for his endorsements. For example, he recently signed a $300M contract with Uniqlo over 10 years - with a clause that will pay him for the full duration even if he stops playing tennis!
Likewise, most successful video game players make their money from their streams, not from prize money. Some may get sponsored. Beyond that though, in video games being "the best" does not necessarily equate to "highest paid" like it does in sports. Streamers earn money for their personality, for making the game fun. Faker probably isn't that interactive or good of a streamer. If you want to compare a streamer to Federer, you'd have to go to someone like Pewdiepie. Pewdiepie earned $12M USD in 2015, and one can only imagine that number has gone up since (unless he's slowed down his content, I don't follow him so IDK). Let's compare that back to tennis. Djokovic, the #1 player this year, earned a total of $15.9M USD in prize money this year. A pretty comparable amount to Pewdiepie's $12M in 2015 (and remember tennis' increase lately, the top player in 2015 probably made nowhere close to 15M). Of course I ignored Djokovic's endorsements here, but I'm sure you get the point.
At the end of the day, a league streamer has a very small audience. Even if league is the most popular game in the world (is it still?), your viewing audience is notably less than your playerbase. Most people that watch League probably only follow a handful of games. So a league streamer has a very small population to draw money from. In contrast, lots of people will watch the NBA Finals, The Superbowl, Wimbledon and the US Open of Tennis, the Stanley Cup Finals, The World Series, etc... i.e. not only do video games have probably only 1% of the viewers to start with, the games cannibalize viewers from each other while professional sports can share viewers.
So - no, professional League players are not underpaid. Not at all.
