He's like the Alfred Hitchcock of music videos: just about any one of the videos he did in the 90s would be something that any video director would hope to have made one day and the fact that he made all of them is enough to qualify him with only 2 features. You can get a complete sense of his visual style, sense of humor, singular creativity and storytelling abilities from his videos.
His ambition is his own worst enemy, and I think both of his features collapsed while trying to do too much.
I disagree. I think that both features work very well. In both cases, I think the film offered more than most people were willing to take. I still have arguments with people who think that Adaptation's third act was horrible. But either you're into what they're doing or you're not. I was and I think it's a near-masterpiece. Malkovich a little less so, but it's still one of the most ingenious films of the last 10 years. If there's any issue to take with those, it's that both films have similarly structured 3rd acts.
I voted that he's proved his greatness because of everything he's done up to now but the problem is he has more potential to lose that greatness. Especially if he does a lesser job with non-Kaufman scripts. Also, if he's not good at picking the right balance of "weird but not too weird" projects, he could end up being the hipster Tim Burton.
That all being said, I'm anxiously awaiting Where the Wild Things Are.