Good coffee and bad coffee?

I have had this question for quite a long time. Since I'm neither an epicurian nor an avid coffee drinker, I can't really distinguish a good coffee from bad. Now, I've been experimentng with Folger's, Maxwell House, Eight o clock, dunkin donuts, and starbucks; I keep arrivng to the same conclsion that my taste buds perceive them as they all taste the same. I told this to my dad one day, and he scolded me for being so "inconsiderate." So please give me an advice on how to taste coffee.