Nice Guy is the idea of “if you work hard enough you get a reward”. This isn’t limited to relationships. I was being a Nice Guy in math competitions - if I just practice enough hours everyday, then I’ll make the IMO, and if not, the world is just screwed up! I was a Stage Two Nice Guy (TM).
Nice Guy is not an unchangeable part of a person, but rather a behavior/mindset that one can grow out of.
Nice Guy is the wrong attitude in life. “Deserve” is the wrong rhetoric. The world doesn’t change because you use the word “deserve.”