Where you do you usually go for buying those old games that can't be found anywhere else nowadays? Do you risk it and try to buy a used retail version or do you go with digital versions like the ones found at gog.com?
I have a good balance of both or so I think. There are several old games like scrabble that I like having the handheld version if so therefore I like to have the computer version as well as the game board version of it. Other games like connect four I have on my phone and computer.
If I want to play really old games like those on the NES or the Sega Genesis or the PS One, I'd just resort to emulation. I've got a couple of emulators installed in my Android device which allows me to play old school games anytime and anywhere I like. If I would want to own an original copy of a retro game, I would just go to Amazon.