The two weeks I rented this when I was 5 taught me more about video games than any game until Mario 64. I will never forget the feeling of being ripped off as the final boss restored his whole health over and over, and the level grinding I did to utterly vanquish them! Beating it was such a rush!
This game is one of the most important games of all-time, and while it is great we got the HD-2D version on modern consoles and Steam, the original release, the MSX port, the superior Super Famicom remake, the Game Boy Color remake, and the 2004/2013 mobile remake should all be preserved and commercially available. No place is better for that than GOG.