A great song is memorable. There are things about the song musically and/or lyrically that stick in the listener’s minds. That’s why they are called “hooks”. If you hear the song “Staying Alive” by the Bee Gees, you will be singing it the rest of the day. That’s a very hooky song in every way. They have started teaching people to give CPR while singing that song because it puts the chest compressions the right space apart and because almost everyone can remember that song.
The song is crafted well. The writer put in time getting the craft right. Usually, the rhyme scheme is solid with close or perfect rhymes. The structure helps the listener follow along. Lines that rhyme are just as good as the line they rhymed with. The song is easy to follow and communicates clearly. Great songs are usually products of great craftsmanship.