I think a great song appeals to older and younger people and it makes you think. It's also honest, and it also doesn't hurt if it's fun to sing along to.
Follow your arrow / Wherever it points.
I know not every song has to be a powerful message.
A lot of times, Im singing things that are observational and am definitely including myself.
Say what you think / Love who you love.
A great song will be great forever - it's timeless and classic in that way.