Recently I discovered an internet "review page" promoted via Adwords
pay-per-click where they rank various products.

My product was ranked at the bottom and my competitor's product was
ranked as the number 1 recommended product. Additionally, the site
claims my product ranks lowest in customer reviews while not providing
any sort of evidence or ranking system.

Upon researching more I discovered that this page is in fact run by my
competitor and this fact is not disclosed anywhere on the page.
Instead they pose as an independent review site.

Additionally, whois information lists this individual as being in New
Zealand while I am in the USA.

Obviously this is a situation that may eventually require legal
assistance. However, if I could cite specific violations I could start
by sending a cease and desist to this individual.

What am I to do?

Go seek legal help.

What you can do may well depend on where you are, where the competitor
is, and how much you can invest in trying to fix the problem.  (From
the posting, we don't know what country you or the competitor are in.)
 One of the better websites for information on internet law is
www.gigalaw.com.  (I am not associated with www.gigalaw.com.)