When I buy a new game I keep it sealed til I want to play it. This way if time passes and I never get to the game I have it sealed.
So I have many sealed games on PS2, Xbox, PS3, XB360, Wii, Wii U, XBone & PS4. I do have a few retro sealed games and I have this guilt about opening them. lol I once bought a bunch of sealed Atari Jaguar games cheap and I opened them to try them out. I told this to a fellow collector and he yelled at me like I committed a crime saying that there was now one less sealed copy in the world. I didn't care, I wanted to play the games.
I don't hunt for retro sealed games due to cost and I do want to play them, every time I happen to get a sealed game I always want to find another loose copy. But if for some reason I find a sealed game at a garage sale I don't hesitate picking it up if cheap, but if I stop at a game store, a game expo or shop online I don't even look at sealed retro games.
Probably the rarest sealed game I own is Nosferatu on SNES.