How far below asking price should I offer on a home for sale right now in the Denver area?

I'm trying to find true comps for some kind of measure, but the fact of the matter is that NOTHING has sold in the last 6 months that could be considered a comp. They've been for sale that long, or longer, but nothing has sold. When I bought my first house in 1995, the realtor told me that a house on the market over 120 days meant something was wrong with it. Probably the price. Does that mean that virtually all homes are overpriced right now, and the market is in the process of correcting? Do I just forget about buying right now, or make a real low offer and see what happens. I wouldn't pay full price for a home right now, even if it were perfect.