Optimism or Pessimism in film/television?

What type of shows/movies do you prefer: ones that make you happy (optimism), or ones with sad overtones (pessimism). Why do you feel that way?

Some examples:

Optimism:

• Avatar: The Last Airbender
  
• Wall-E

Pessimism

• The Dark Knight
• Death Note

the pessimistic stuff makes me laugh and the overly optimistic stuff make me want to vomit

pessimism is the best, at least it is the truth!! and plus dark comedies are funny!!!

A mix is always nice, but sad overtones are overall more truthful and meaningful.

Pessimism, mostly, sometimes a happy ending isnt right(WAR OF THE WORLDS) I love sad endings, but if theres a happy ending, and its fine I like it too, just aslong as its not stupid.

Optimism is good of course. But I love dark, pessimistic stories.

Optimism always makes you want more, thus making you kind of sad.

But how is The Dark Knight pessimistic? It's a little bit of both.

I can't choose, I love horror (The Descent) and tear-jerking tragedy (Grave Of The Fireflies) but I love the Pixar animated films (Finding Nemo) and the light-hearted ones like Juno and Little Miss Sunshine too.

Pessimistic stuff most of the time.

I like both, but I prefer happy stuff like comedies.