Hard to rate. They all have their strengths and different criticisms that might keep them from being someone's top pick. Spielberg has made more of my favorite films. Cameron has a stellar win rate, but isn't very prolific and now seems to be confined to making movies about blue people that I'm not too interested in. Fincher is probably the most technically knowledgeable. Nolan is impressive when constructing a movies plot and pace but sometimes his characters fall short. I'm super interested in how Coppolas Megalopolis turns out.
Ultimately I'd probably give the nod to Spielberg simply because he's made the most movies I can watch over and over, and at the same time he's made incredible powerhouses like Schindlers List and Munich. He's shown the most range, and has incredible techical ability, even if he probably has also amassed the most misses as well. But that comes mostly from being productive, I think.
I'm really curious in what Denis Villeneuves resume will look like in 15 years time. So far he hasn't had a single misfire.
