WordPress for Lead Gen – Search Directory Site?

I am trying to decide which open source CMS is the best way to build a new Lead Gen – Directory Search website. Something identical to sites like or

I would like to use an open source CMS like WordPress but have been given conflicting opinions of whether it can be done. Most say I need to have a proprietary CMS developed to mirror what these sites are doing.

What are the thoughts of all of the WordPress Gurus out there regarding this dilema?

All opinions are much appreciated!