As someone notorious for doing this myself, I'm going to give you the advice I am trying to follow - show someone. I've found that occasionally I will dig through old work and find myself pleasantly surprised by how good it is, because I'm distanced enough to, in a way, forget that it was mine. It's a nice sensation because it proves that you are capable of doing well. Sometimes we need reminding. I think any old stuff should be examined. It could be that it isn't as good as something you've written more recently, which is often the case, but there may be a line, an idea, or a character in there that you want to return to, or maybe steal and use for a new thing. Cannibalise your old work and don't feel guilty about it. Got characters with no plot, and a plot with no characters? Combine them. Magic might happen.