ExtremeTech.com has a good set of reviews on many of the major RSS readers. The article will give you a good way to get up to speed on the various reader options. The article gives the highest score to FeedDemon, which happens to be the RSS reader / news aggregator I’m using these days.
A brand new beta of FeedDemon was just released and makes some nice improvements. If you are shopping for a new reader or want to try another one, I recommend giving FeedDemon a try. Note that it is still in beta, but free. When it is “officially released” expect that it will no longer be free.