What you listened to in your formative years has a great influence on what you like later in life. I've always "exercised" my musical tastes, so mine should be flexible.
Also, unless you have good stores near you, you need to stop shopping in stores. They only carry the most generic "likeable by the most people" type music, which is useless in today's world of growing population and diverging tastes. Try: emusic, iTunes, cdbaby, amazon, pandora, and so on, to discover what kind of music you really like.