I'm in the minority (maybe not?) of people who can't stand dirty, greasy, sweaty controllers, even if all of that comes from myself over time. When I buy second hand stuff, I clean it thoroughly, controllers in particular.
I usually take them apart and clean all the bits separately in soapy water. If it's small cleaning, some wipes are enough I guess. But yeah, wash your hands regularly kids, it's just common sense.
And I can't wait to see those hostesses cleaning the controller after each person has played at the TGS. Must be so weird in person.