Disclaimer:The following is written as pure speculation, and providing a counter-argument to the above points. These are not necessarily my personal views.
Anyways, the argument above by Domin against Intellectual Property is usually referred to as the Abandonware argument. Simply put, if it's all been abandonned by the company, it should be public domain.
However, the tricky part becomes in defining what abandonned actually means. Is it 10 years after release? 20? 50? Is it whenever they stop producing copies? What about sequels/spin-offs to a franchise/brand? And remixes/redone games? There are endless possibilities of variants that could or could not be done.
One critical issue is the lifespan of the storage used to preserve these old games. This could vary from company to company, depending on their good/bad system. Most anyone would agree (except for the people only in it for the money), that in an ideal world, if a game is never going to be made again, and the only copy is starting to deteriorate, then it should be made public to be saved. However, what if a company trashes their copies the day they ship? There is no law requiring them to keep the thing.
Another issue is the way games work. Just as history repeats, styles of games go out of fashion and into fashion again. This is especially true with the propogation of older technology into smaller forms. A good example of this is the Nintendo e-Reader. Some of these games have been 'abandonned' for over 15 years, but now Nintendo is trying to make an extra buck with them.
I'm not pretending to have some ultimate answer to this. IP is probably one of the most difficult laws to write, so that it is fair for everyone. Just because something currently isn't in prodcution, does that mean a company can no longer make money off of it?
I have been hearing some theories recently how the Music and Movie industries will eventually become like the Book industry, with the production process becoming cheap enough for more competition, in addition to better book-keeping processes in libraries. Maybe we will have a 'Games' section in the libraries of the future. Who really knows?
For further information, please see more general topics such as government-granted monopoly.