When we start watching a new TV series we try very hard not to judge it until we've seen two episodes. The first episode, the pilot, is usually doing a heavy overload of exposition, and it's not fair to judge by that alone.
For a movie, 20 minutes is the key - if it hasn't made us want to see more by then... *click*. To me, this is like the "rule of thumbs" for a résumé: If your prospective employer wants to meet you, they will probably decide that by the time they have read from the top of the first page of your résumé, to the point where their thumbs rest as they hold the page. So there you go, you have maybe 3.6 inches of a letter- or A4-sized sheet to make the impression.
If you watched this show and continued to the end, would you please tell me why?