the only reason why current DDL sites aren't that popular is because they're not that good themselves in the first place. I know I'd never go look for something on a site that links totally lame sites from their Index.
I completely agree with Suicidal.
Your aim should be to make users happy. Just aim on that and your site will be fine.
Some suggestions are:
1.Don't use ads
Once you have loads of traffic, just put up a small banner in the sidebar sell it for 100$ or something like that.

2.Don't sign-up for affiliate sites.
Most DDL sites redirect you to these affiliate sites, or give you false links stating 'WinRAR download FREE at sharingzone.net' or something like that.

Make a Clean site without Youtube, or IMDB links for every movie.

Try to keep out duplicates.

It's better to have two links to different products, than having 200 links to the same movie.