amok: I'm not going to complain about it, in fact many of these sites are good for game preservation. But plazas be aware of what it is, which is piracy. Abandonment is a fancy name for piracy where the right holders don't care enough to prosecute. So by providing these sites and the way you word it, you are in fact promoting piracy, there is not two ways about it.
So do as you like, I want judge you for it, on fact I do it myself, but I also do not pretend that what I do is something else than what it really is.
Ogdin: That must be sarcasm with the horrible grammar but I'll go ahead and take it serious and say that Abandonware (a euphemism if you must) is exactly that, a abandoned product, doesn't really work right and on modern OS some might not work. Piracy is a term created by the multi-billion dollar game publisher/developers that make shovel-ware which should be a crime that crap costs money, GOG gained popularity since people would pay money for abandonware that worked...
Of course what is or isn't piracy is up to the individual, I say if a game cannot be bought digitally except by 2nd hand that game is abandonware since no money would go to the developer/publisher, of course with GOG selling abandonware games things change but a GOG game =/= Abandonware game of the same game, GOG works to have the game work on modern systems or add new features, improvements to make it the superior version.
Off course piracy is "not up to the individual", it is quite clear and straight forward. It is defined both legally and commonly. Piracy is "unauthorised use or reproduction of another's work", that's all there is to it.
Abandonware is not authorised, therefore using it is piracy.