I've been wallowing in computer game nostalgia, playing old arcade, NES and Apple ][ titles. The emulators are fantastic. And you can download the complete history of Nintendo in one easy 250 meg archive. Arcade games have a fantastic database.
Playing old console games is easy, but playing authentic Apple ][ games is hard. They were copy protected with bizarre data layouts, manual lookups, code discs, etc.
Copy protection failed to protect the companies' profits, but it makes it harder to preserve Apple ][ history. The popular Apple ][ archives don't serve the original game; they serve cracked versions. They mostly work, but if you're into pristine preservation it's not quite right.
I wonder how folks will play today's PC games in 20 years. I think the DirectX API will make emulation easier. But the games are still copy protected. There are emulators for today's PC CD protection, so maybe preservationists will be able to play the original. And there are cracks too, but most are rips that strip out a lot of game content to make the download smaller. Ugh.