I have to admit, that I have mixed feelings about Ben Stiller. (Which is a much more positive reaction than you could get out of a lot of my friends.)
I really liked Zoolander. Was it stupid? Oh, sure. But it was also extremely funny. Stiller was sort of lampooning his own brand of spoiled narcissism -- which worked. And there were some legitimately good jokes. (Like, say, the "freak gasoline fight accident.")
Moreover, I've always thought that The Cable Guy, (which Stiller directed, but didn't star in) was seriously underrated. The idea that cable TV is like a smothering, ingratiating friend (Jim Carrey) who tries to take over your life was sort of brilliant. (And sort of true.) Stiller kept things dark and stylized, and I really admired Jim Carrey's Jerry Lewis-like performance.
There have been other movies that Stiller has done which I've admired (Flirting With Disaster), or half-admired (Along Came Polly).
But, yes, I will also admit that a healthy percentage of his shtick is whiney and self-pitying. I find the "humor of embarrassment" pretty unbearable. And plenty of his movies simply stink. (No man, woman or child associated with The Heartbreak Kid should ever be entirely forgiven.)
Which brings us to Greenberg....
All of the familiar Ben Stiller tropes are there. Roger Greenberg is just as much a vain curmudgeon as the character Stiller almost always plays. He is a jobless, middle-aged man who just had a nervous breakdown, and is filled with complaints about youth, traffic, pet taxis, and the overly loud customers at restaurants.
Like Saul Bellow's Herzog, Greenberg's complaints take the form of letters. But unlike Herzog, who is trying to commune with Martin Buber and Friedrich Nietzsche, Greenberg chooses more earthly correspondents, like Michael Bloomberg and Starbucks. And most of his complaints/observations are not that much deeper than the kind of thing Jerry Seinfeld used to joke about in his standup.
But this Ben Stiller is a few shades darker than the one we've seen in the past. He nails the general angst that a man feels at the age of 40 when his hopes and dreams look suddenly unlikely. (Greenberg's dream was to headline a rock band. He became a carpenter.)
And even though this character is meant to be an asshole, he's not entirely unlikable.
Why? I'm not entirely sure. I think it's because he sort of accepts the fact that he's such a jerk. But I think another part of it is that all of us feel, at times, possessive of our privacy. We, too, seethe with hatreds and complaints when we're forced to meet with other people. We have no patience for the larger world -- and, I hate to admit it, but Stiller gets that down very well.
There are a lot of other elements in this movie that are worthwhile; Greta Gerwig is an overly sweet (and extremely down-to-earth) love interest. She's a good 15 years younger than Greenberg, and similar in that she has a certain purposelessness to her life. But Gerwig doesn't seem all that bothered by this. (Maybe she'll be different in 15 years, though.)
She is an excellent foil for this extraordinarily selfish man. It's painful to see how badly he treats her. But, probably true to character. And sometimes that's the best thing an actor can do.