Very hard to find good kosher pizza, most places are terrible. But, there are some really good ones:
Brooklyn:
1) My Favorite Bagel
2) Mendelsohn's
3) Pizza Time
Manhattan:
1) Bravos (by far the best kosher slice. Even guy from Barstool gave it a really high score).
2) Sabas
5 Towns:
1) Bravos (Queens)
2) Upper Crust
3) Josh's Brick Oven
NJ: not familiar with many places there, but had EJ's and didn't think it was good.
West Hempstead: Hunki's is very good
Crown Heights: No good pizza there.
Miami: I miss Shem Tov's, that was really good. Miami doesn't have good pizza anymore.
Crown Heights, Benny's (formerly Pomodori)
used to be good. Recently had tomato basil slice from them, crust went significantly downhill, topping was good. I find Holesome/Sauce 'N Cheese inedibly sweet, and Kingston Pizza isn't that much better. Haven't tried Calabria.
In KJ I actually think Yossi's has an amazing crust, the sauce is OK, but the cheese - well there's just waaaay too much of it, and it's dripping oil.