anallawalla - 2:28 am on Sep 8, 2009 (gmt 0)

The same rules of SEO apply.

If it is a major Yellow Pages type of site, it has a great deal of TrustRank and its pages will do better in very competitive niches such as Adult than you'd expect. Such sites have a lot of quality backlinks, at least to its home page. A humble "SEO directory" for exactly the same listing might not show up at all unless it has exceptional SEO, both on-page and off-page.

For a generic listing, it all depends on competitiveness of the search term, hence I say that the usual SEO principles apply.