I guess every city has to have a good pizza place. Mumbai has a few too.
1. Don Giovanni in Juhu(undergoing a renovation) and Worli has some really good pizza. Its not as crisp as some of the other pizzas out there but definitly worth trying. I reccomend their Pizza Ai Salami which has four kinds of salami and lots of cheese.
2. Indigo Deli in Colaba has a really good paper thin pizza. The crust is nice and crisp if thats something you like. I dont think they have a fixed menu and serve up a weekly special salami on their pizzas.
3. Pizzeria at Marine Drive/Powai and Versova has more "consumer" pizza and they deliver. The quality is dipping to be honest though its still the best pizza delivery. Their pizza has an Indian twist to it and I guess some people who dont enjoy authentic pizza may like Pizzeria more.
Mangi Ferra in Juhu has a woodfired pizza oven but their Pizza is crap. Not authentic at all. Also worth mentioning is the coffee shop at the ITC Grand Maratha where I have had a decent pizza. Open 24 hours quite good if you get the munchies in the middle of the night