Futurama is like the only mainstream adult animated show at the time that actually attempted to tell genuine emotional stories.
I consider that an achievement in the era of nothing but comedies... Even if itself is a comedy lol.
Reading these comments show that people really don't understand what they read.
Garp is not a sell out. The Navy is a massive organization and it has been shown time and time again that there are good people in their ranks. Garp believes in the justice that the Navy stands for at its foundation. He refuses to protect the CDs (hence why he never took a promotion) and he uses his status on the inside to train soldiers to have morals and truly protect the world within the law with righteousness. He's going a very slow (and maybe naive) route, but trying to change the Navy from the bottom up.
Dragon, however, decided to forgo that route. It wasn't fast enough and he had an absolute view that anything connected to the CD and above cannot be trusted to fix the world. He chose his path to risk his life and abolish the unfair system as a whole. He understood the risks that would place upon his family and left his child with his father, whom he explicitly trusts. When it comes to a revolution, sacrifices have to be made in order to fully commit and make the change for your loved ones and everyone else. He decided to be a "bad father" in order to create a better world for his son and everyone else.
Luffy, my boy, is just pure. Easiest way I can put it. He has a sense of morality (except when it comes to meat) and believes everyone should have that freedom. He's not aiming to save the world or stop the tyrannical rule, but he will not allow the freedom of those who have helped him to be trampled upon. He has shown that he does not want to be a hero and you should be able to stand up on your own two feet, but if it's too much, he will step in to help. His Savior type is tied more to destiny and fate than anything else. Right place, right time.
Each is trying to change the world in their own way. They each will, oddly enough, rely on each other indirectly to accomplish their goals in the end.