Why would you ever want to play a video game in a language you don't understand? Once you hear Half-Life's G-Man, Metal Gear's Psycho Mantis, and Portal 2's Space Sphere speaking German you'll understand completely.
I thought I knew Mario, but I was wrong. Apparently Mario robs banks, dresses up like a cowboy and crushes koopas while waving the Union Jack. But why would Mario do such things? To teach English of course.