Homemade nut and/or nutritional yeast cheese is great, but fake cheese rules too. I've tried quite a few brands and flavours, and here is my verdict for the best ones.
The best for eating melted:
I have found that the Montery Jack flavour from Follow Your Heart is the absolute best vegan cheese on pizza. It melts quite soft, so you have to cook it until it bubbles and browns a bit (always good) or it can be too runny, but even then it tastes great. The mozarella flavour is good, but it just tastes sort of butter-y.. the jack has a bit more kick.
The best for eating cold, unmelted:
Sheese is very expensive but pretty damn good. It is the only vegan cheese I've ever had that tastes really good in a cold sandwhich. It is very firm and has a great texture. I doesn't melt very well, though. It doesn't spread out like FYH does. My favourite is the Smoked Cheddar flavour, but I'm sure they are all great.
Best parmesan substitute:
I'm a big fan of the Galaxy Foods brand parmesan.. as far as I know no one else makes a parmesan substitute.. but that's ok, because this stuff rules.
Best cheese slices:
Tofutti slices are the greasiest cheese I've tried, so I don't eat them often, but they are pretty yummy. Try them torn into pieces and melted on pizza. The flavour is quite butter-y, but sometimes that's what you're going for.