I'm not sure if I'm sure that I'm sure that Mario is the good guy in all this...

I mean he lays waste to a kingdom of Goomba's and Turtles who seem to ignore him completely (unless you touch them, which I mean, come on, you touch a guy thats crossing the line...) all the while destroying bricks and depleting the land of all its precious Power Mushrooms, Toonki Suits, and Fire Flowers. Overlain in this trail of terror is the "love" mario has for "princess" peach. But if you read the description of Bowser from his very first appearance, it says that the so called Mushroom Kingdom was once HIS kingdom! So Peach, and her father who I am guessing is called "King Toadstool" invaded and or usurped the throne from Bowser in the first place...When Bowser kinaps the "princess" he is in effect attacking the corrupt Toadstool regime in all its Tyrannical power. Bowser is like a Polish Warsaw Ghetto Freedom Fighter. 

enter mario...

I'll start with the fact that he punches Yoshi in the head everytime you press the B button. Thats just animal cruelty right there. 

Mario Mario is a mercenary. From our world. A cold and calculating murderer whose only goal is the total annihilation of all Bower's forces. Using unnatural powers over flight, flame, and plumbing, and also apparently an innate ability to breathe underwater, Mario (and his loser Brother, Luigi Mario) systematically commit ritual genocide throughout the many worlds they decimate. As plumbers I'm sure they also price gouge for tightening and general repair. They are also Italian.

 I'm pretty sure that they were also responsible for 911. Here is more photographic proof.