%%- If the tune isn't good, the song can't be good no matter how great the lyrics are. But if the melody is ok, good lyrics could help bring out the flavor and turn it into a great song.
MONA LISA is an example. I had thought it's only so so but once I knew the lyrics, it's in my favorites list.
"Do you smile to tempt a lover, mona lisa? Or is it your way to hide a broken heart? ........ ........ Are you warm, are you real, mona lisa? Or just a cold and lonely, lovely work of art?"
The lyrics perfectly match the melody and no wonder it was number 1 song for 8 weeks.