Atlantean might stand alone OK, but for my gaming preferences, PP and Insanity are not games that I think stand alone as well. I can only speak for myself, here, I guess. I would only pay for those gameplay experiences as part of a collection. I just don't find Pacman and Berzerk engrossing enough to want to own them as discrete titles. (Note that this is not an indictment of your programming and artistic efforts. It's just my opinion on the underlying, original game.)
And since I still don't have, and still can't afford, a CD attachment, I would want something on a card so I can play it on my Core.
That's my very selfish, self-centered 2 cents.