Is James Cameron the greatest filmmaker so far?

The problem is, your metric is ridiculous as it has caveats immediately discounts a massive amount of world class directors throughout history.

Therefore the title of your accolade should be "Greatest filmmaker who writes his scripts"or something, not "Greatest Fimlmaker".

I could start a thread saying "Who's the Best Director ever?"

Then in the opening post, I could write, by the way, to qualify, the Director's must be aged 56, born in Houston, Texas and have a wife called Christina. But that would be just as ridiculous.

It seems like a lot of the discussion in this thread comes down to you pointing out different reasons why Cameron should be considered the greatest filmmaker and other people arguing why those reasons don't support your argument. This is especially true of the screenwriting issue because you use that as one of your main arguments for why you think Cameron is the greatest - on its own, this is an acceptable opinion, even if it is not one that most of us would agree with ourselves. However, the real problem comes from you conflating your high opinion of Cameron with the fact that he writes his own films and using that to argue that directors who do not write their own films are fundamentally inferior to directors who do. This goes beyond merely defending Cameron and into attacking other directors - you're effectively tearing down many other filmmakers just to build up Cameron. This is why people are disagreeing with you so strongly - not only is your stance on writer-directors provocative, but the logic behind it isn't very sound in the first place and seems very contrived. Even those in this thread who like Cameron's films are willing to admit that his writing ability is significantly weaker than his directing ability. At the very least, his writing is not strong enough that it should be used as evidence for him automatically being greater than other "great" filmmakers like Spielberg or Scorsese. The opinion is valid, but the factual arguments used to uphold it are not.

__________________
Iro's Top 100 Movies v3.0

I think James Cameron's writing is top notch just like his directing. He has proved himself he can write anything from sci fi- romance to comedy sprinkled with some little drama. I see not evidence that suggests that his writing is sub par.

Is he the greatest so far?

It's fine if we're talking about subjective opinions on a subject that invites it (which is definitely the case when it comes to discussing art and film is definitely an art form), but things become complicated when you try invoking objective concepts like proof or evidence. By keeping it purely subjective (especially in using the words "I think") it stays okay and we "agree to disagree" as it were, but saying that you "see [no] evidence" is a problem. Seeing as you are the only person in this thread who is arguing for Cameron being a top-notch screenwriter (and you were the one who brought that up in the first place to support your "greatest filmmaker" claim), the burden of proof would actually fall to you instead and you would have to provide evidence for your case to all of us. Even by that standard, you haven't given us much of a concrete argument that he is a great writer beyond some rather circumstantial claims about his creative breadth more so than depth (by your reasoning, I'd counter that Ed Wood proved that he could write sci-fi, horror, and melodrama, but that doesn't mean that he was good) and a contrived claim that writer-directors working off their own ideas are inherently better filmmakers than those who adapt sources or work off other people's scripts (which many have found to be a disagreeable perspective and not without reason). In response, people have pointed out their many actual complaints about Cameron's writing, especially when it comes to plot, characterisation, world-building, and so forth.

The point I'm trying to make is that, by trying to "prove" that you are right and that the other side is wrong, you're turning this from a discussion into a debate and that just won't work for a subject like this. You say that you see no evidence but, really, how can you? Conversely, how can those of us who disagree with you see any evidence for you being right? That's the problem with this thread - both sides are trying too hard to "win" a debate that is technically unwinnable. Many people have argued against you so far but the fact that you can shrug them off with a simple "well, this is what I[ think" should indicate that this is not something that can be objectively proved regardless of how many people are on one side or another. I mean, if you'd set up a "yes/no" poll in the first post, chances are it would be an almost unanimous "no" but that wouldn't necessarily be right or wrong. Accepting that is important, because otherwise what are we even trying to do here?