Well, I love pizza, but I can't really eat it on a diet because I don't just have "one slice" lol. I really can't even be near it. The only thing bad it does to me is a cause a breakout the next day.
Still, a healthy pizza idea is getting low carb wraps(mission carb control are good), putting in a couple slices mozzarella, oregano and basil, along with peppers & mushrooms or whatever you like, and tomatoes. You can wrap them up or lay them flat -- warning though, they can get watery and messy if you use fresh tomatoes instead of tomato sauce, like I do. You can cook the tomatoes first, so that might help.