It doesn't matter if you're Bowser, Mother Brain, Dr. Eggman, Hitler, or Mike Tyson, the motivational speech is always the same, and it always gets you absolutely nowhere, as this CollegeHumor clip readily demonstrates.
I think the main problem lies in the fact that it's only one man, generally assaulting a fortress made to withstand an entire army. They never plan for the one-man army. Someone should start up a business, offering one-man army proofing to video game villains. They'd make a mint. Hell, they wouldn't even have to be particularly good at it, as no one would be left alive to complain.