Its not directly in LA but Village Pizza in Big Bear is the best pizza I've ever had. Nothing beats their crust, their ingredients, and the experience of wolfing down a large pepperoni and a pitcher of Sierra Nevada after a long day on the slopes.
+1 for Georgees in La Canada...I used to ride my bike there for a slice and video games as a kid.
I'm very fond of Whole Foods Pizza. You can go in, order your pizza, then do some shopping before picking up and heading to the register. The cook it in a gas fired, brick and range top oven. I love the fresh taste, because you can watch as they cook everything right in front of you. Also they still taste like the flour they use to keep them from sticking to the oven. The pizzas are about 2 1/2 feet in length and a foot wide. Quite Delicious.
Not in in but not far from LA,: Petrillos in Glendora, Pizza Port in San Clemente, Speaking of beer crust not only does pizza port have amazing beer they give the option to have crust inwhich they use their spent beer grains