I good with 2 or 3 good quality toppings. Tatoosh is right. Quality over quantity is how I feel. I wrote an article for my local paper last year on pizza toppings. I'll post it if I can find it but it always comes down to defining a "topping". To me, sauce, cheese, salt and pepper is a given. A topping is something that goes on top of your plain pie. My mother loved the "everything" pizza. Pepperoni, broccoli, ham, green pepper, hamburger, onion, olives, mushrooms etc,etc ad nauseum. I couldn't make heads or tails out of it! It was a train wreck of a pizza to me. WAY to busy tasting. WAY too much going on to appreciate.
I also think that the way you address the toppings is important. They should be exceptional before they go on the pie. I would be really interested to see how others treat their toppings pre pie. I'm a little neurotic about it. Only because I've eaten too many cheap, thrown together, lazily made pizzas. One bite and your like "these people don't care about what they're doing"
It would also be interesting to see if others have found any unique ways that they get flavors to "pop" on the pie.