I think the best lyrics are lyrics that tell a story that is very personal to author but everyone who reads them can relate to it. I know it's a cliche but most "love songs' fit this mold. Everyone has been in love, and even though the author has a different experience with love. People can still relate to it or most of what is said in the song.

Of course there are other topics than love. Even lyrics that are more of a storyboard, especially horror and sci-fi types. Storyboard lyrics make for great threatrical songwritting, my fav.

Also, when the lyrics utilize senses other than feeling and sight. I think the connection of the lyrics to the listener is enriched. Lyrics that touch on smell, taste, hearing, touch, and the way the body might react to the situation the song is presented in. These lyrics are much more powerful since the range of connection is greater. Even though the listener wouldn't have been in the exact same situation, they can always relate to the sense stimulations. It also breathes life into a song.

I like reading short stories and poetry rather than other songwritters for inspiration.