If Lord of the Rings is the greatest Fantasy story ever written, told and eventually brought to the screen, than there’s a good chance that Gandalf the grey or the White is the best Wizard of all-time, seen or introduced on any medium.
While A Song of Ice and Fire fans might argue the LOTR claim for best story ever, it doesn’t really have a wizard in the way they’re usually perceived. So there’s no epically awesome character like Gandalf, or at least in the way Gandalf is awesome.
What makes him so great, besides being a wizard? It’s hard to put a finger on what Gandalf does “on-screen”, because after his transformation from Grey to White, there isn’t a whole lot he actually does in order to make Frodo accomplish his quest. But he has the sort of presence that helps things get accomplished a bit more smoothly.
As this brilliant infographic from LOTRPROJECT clearly shows, he actually prefers doing nothing, and simply overseeing events while others do the actual dirty work.