Short Version: Snyder=Amazing director chained to uneven quality screenplays.
History is selective, the best directors are the ones who make the most classics, not tell the best stories (that's the screenwriter's job). They only appreciate as time goes by. Snyder is the former.
Film is fluff. Fluff is the cool use of cinematic technology. People dissing fluff are dissing film. The best directors know this, and add literature to justify their fluff, rather not creating something people want to see.
Art is controversy. It is always being discussed on whether it tells the truth or not, validates the viewer (ego based criticism, but it's everywhere), or says anything at all.
Zack Snyder makes artistic fluff, and hopes people see the stories.
That's what great directors do. There are very few literary minds that direct (early M Knight, Bryan Singer, Chris Nolan) but even fewer directors who cherish the art form (Wachowski's, Malick..Spielberg on a good year...)..like I said, hard to find.
As the genre is still forming (Avengers/TWS/DOF), Watchmen's deconstruction is validated, and critics like it more.
If Snyder stealthily combines Kingdom Come with Tower of Babel and substitutes the threat of language garbling with Doomsday coming to Earth, with Batman as the strategist who uses his knowledge from his Kingdom Come nightmare (Part 1, and yes, I much prefer that to the Pulp Fiction twist in the book) to give the JLA the ideas to beat Doomsday, it will be the best thing to the medium.
The Watchmen crowd will love part 1, the Avengers crowd will love part 2, and the critics will be honest for once.
And yes, I wrote to him, hoping he or WB reads this. It's really a terrific idea, and the Avengers could do something similar of Zack doesn't beat them to the punch