Hmmm, Doom, Doom II and Star Control 2. These games are just so mind boggling fun and simple to play, well maybe not Star Control 2, and enjoy even today. Since they have stood the test of time for me they are the only games I would consider defending. Mainly against graphics attacks, those are just bogus.
Otherwise I haven't really considered any other game to be that grand that warrants protection from attacks. I can see the good and bad points so I'll be happy with people who pick at the bad points. Just means a patch has a bigger chance to fix that issue. Don't get me wrong, other old games like Planescape: Torment are some of my favourite games, but they do have flaws that I can understand from certain perspectives.
Other modern games are really fun as well, but I can see them fading away as better games are released. Or their unique mechanic becomes stale.
Can't really bash Doom. Run and gun. Call it simple but it is fun.
Star Control 2 gets me story and exploration wise.