I was watching an old Cheers episode today, and I realized that both comedy and tragedy revolve around the character flaws of the participants, and got to thinking about the difference.
The difference is CONSEQUENCE. In a comedy, things turn out more or less alright, despite the vanity, stupidity, cupidity, and shortsightedness of the protagonists. In a tragedy, it all goes to shit.
We live in a comedic age, which in having forgotten history, has forgotten how quickly comfortable lives can become miserable.