If we are talking about art, the better ninja turtle, or who has the more fabulous name, then Michelangelo. If we are talking about who has made the greater impact on history through their contributions to multiple disciplines, then Leonardo. Both were masters ahead of their time.
Wait a minute Jacqueline! Leonardo not only painted the Mona Lisa he knows science (mostly anatomy),engineering and architecture.Leonardo: Painted the Mona Lisa
Michelangelo: Painted the Sistine Chapel, sculpted the David, sculpted the Dying Slave and the Bound Slave, sculpted the Pietà
I think there's a clear winner here.