Good Riddance (Time of Your Life) (which is the correct title
) by Green Day is a good song, but it wasn't meant to be a "feel good" type of song. It was written to be, not spiteful, but I can't think of a better word. Everyone interpreted it to be a happier song (myself included), but I saw an interview with them and it was explained there. And now we all know the truth.
Sorry I don't have any suggestions, I don't think we even had a graduation song, just a prom song.