That is a great question. In the original trilogy, without prequel context, he often makes overtures to Luke about them ruling the galaxy together. Otherwise I don’t think we see a lot about what Vader wants until later when he’s dying. I think then he says something about Luke having given him hope or something, I don’t remember perfectly.

So from the original trilogy alone I think it’s not 100% clear what Vader wants, but there are strong indicators.