I seem to have a strong preference for "Happy" and upbeat pinball machines. I would put The Simpsons Pinball Party, Scared Stiff, World Cup Soccer, and Fish Tales in that category.
I can think of a few darker pins like "The Hobbit", Alien, Walking Dead, and Dracula which are solidly in the opposite category and I don't really care for regardless of playing experience.
What would you guys say are the happiest and most upbeat pinball machines?