It's hard to say, I picked one of my favorite articles for the MAD vault. Which is one of the features of the Magazine so they don't have to actually pay artists or writers to come up with new stuff.
My own personal tastes don't really have an effect on whether song is a parody target or not. But having said that, I try to pick songs that I actually like because I realize that I have to live with these songs for a long time, from when I'm working on them in the studio to possibly playing them onstage for the rest of my life. So I try not to pick songs that I know would drive me crazy.
I suppose I had my rock star fantasies while I was singing into my hairbrush in the bathroom mirror, but I never really consciously said, 'OK, this is what I'm going to do for a living and I'm going to be Weird Al.'