He's the voice of Homer Simpson, Grampa Simpson, Barney Gumble, Groundskeeper Willier, Mayor Quimby, Hans Moleman and Krusty the Clown. Hey hey! What else matters? He's won 4 Emmys for his voice-over work.
As far as I'm concerned, that's the best possible contribution to society after the guy who created those characters. Happy birthday dude! Rock one!