Some songs are instantly likable, often because they are simple and their hooks are easily grasped. I would compare them to children's songs. You know the tune and words, and may find it fun to sing along with once in a while, but as an adult, you're not going to get anything deep out of "Row Row Row Your Boat" over the long run. Enjoyment tends to decrease with time and exposure.
Other songs are not instantly likable, but as you get to know them, they reveal wonderful, joyous tidbits and layers, and your enjoyment grows with time and discovery. They are not so simple as to be grasped immediately; they must be learned and examined, just like any other advanced subject.
There is nothing wrong with popular, easy art, and it's not really a matter of acquired tastes being superior, just that acquired tastes can ultimately be far more rewarding to the individual, as they provide lasting, increasing reward in exchange for your effort and attention.