If a home doesn't sell in three years, there's a problem. Few sellers like to hear it, but price fixes everything. From a difficult location to the condition to the slumping market, pricing will fix it.
From a buyer's perspective, the "value" isn't there. And have you checked your address on Google or Bing? How many web sites did it come up on? Are the photographs plentiful and appealing?
Obviously, there are things outside of price that can also impact the ability to get a home sold but your agent should be addressing these with you on a weekly, if not monthly basis.