I think there's some confusion in this thread between songs that are intrinsicly bad and songs we're just tired of. For example:

I love The Streets of London...and it's safe to say I haven't heard anyone play it in a session for two years.

Also, I just rolled out the Fields of Athenry at a small informal session last weekend. There were a few musicians who have been going to sessions here for a looooong time...and they had never heard it before. I just assumed that if they've been playing Irish music they would have been familiar with it...who knew.

Neither song is poorly constructed or has bad lyrics...but they ABSOLUTELY could get lame from being over-played.

At the risk of being shouted down by people whose opinions I value, I'd like to echo Don's point: I still think The Wild Rover has a place in the set list. We are talking (broadly) about folk music, and the folks in the pub always join in when it's played. The only people who don't like it seem to be folk musicians...which smacks a bit of snobbery, IMO.

...but for some reason, no one ever requests Kum-by-ya