I think part of the question though is also, would they have been as popular as they were without piracy, which does provide some advertising benefits through audience exposure. It is easy to say a really popular game would still be popular without piracy, but some lesser known games might never have gained any attention at all if there weren't enough people spreading word about it. Of course trying to quantify the sales and word-of-mouth benefits from that sort of thing is extremely difficult.

It’s difficult enough that perhaps we should leave it in the academic / ideological argument space and focus on whether copyright owners should be able choose whether or not to give away for free in the hopes of a net win.