Being a musician who plays live and has attempted to submit music to the industry I know exactly what makes a hit song. It's called pop. Pop music is the same regardless of what music you apply it to. It fallows the 3 chord formula. Use only 3 chords because it is easy to process. More people listen to Lady Gaga than Dream Theater because Gaga songs are all written using the pop formula. Dream Theater is a progressive band who uses the entire spectrum of notes, styles, and has a tendency to write songs that last for 28 minutes...most people who listen to pop listen to 1 song until they are bored with it, then they go to the next song. And said song is only 3 minutes long....
Chorus, lyrics, bridge, chorus, lyrics, bridge, chorus, (solo optional) chorus.
This is the formula for metal bands wanting to be on the Jagermeister Tour. Your music must conform to a formula in order to be considered. Minimum of 3 chorus parts per song. Go back thru your fav music and count the chorus parts (usually the song will start with the chorus riff but does not count because of the lack of lyrics) if you hear it 3 times...you got pop on your hands and you need to listen to a wider range of music, there is always better out there.
Now...this formula has not been around forever, it is just in recent times this has come to pass, but the record industry has always tried to find ways to sucker people into their wallets. Like any other business they have schemes and plans to wrestle your hard earned dollar (unless your a kid in which case get a job you lazy leech) from your hands.