It is really interesting and at least partially unique to games I think, how modern controls or other changes can "ruin" older things for you. There's a lot of zeitgeist in gaming, certain things can be very hard to appreciate for a number of reasons--genres become over-populated, control schemes change, expectations in graphics, storytelling change, performance issues happen.
I still love it to this day, but I can certainly imagine someone growing up on 120hz PC games going back and finding Ocarina of Time and it's 20FPS nauseating for instance. I personally find a lot of NES games hard to appreciate because the controls are awkward at a very basic level. Mega Man and SMB3 are huge exceptions, but stuff like Kirby's Adventure (which at least looks lovely) is really clunky. I enjoy Kirby's Adventure still, but I really like the Kirby series and it looks so good, I'm not as kind to lots of other NES games.
And lots of early 3D games have extremely weird control schemes that must have made sense when they were novel or at least been no worse than average, but now that 3D control is pretty standard (and I mean, it's not hard with dual analogs) it can be weird to go back.
Which is where the Tomb Raider thread references are being made here (although SOME people bringing that up don't really want others seeing that to read thru that thread...)
The "fancy graphics goggles" can be more blinding than the nostalgic ones.
I like "Infatuation goggles", myself.
Outdated ideas do not mean a game isn't as good as it was before, or that isn't not as good as modern games
A lot of indie games use "outdated" ideas and styles that often ape older games, but to say they're all worse than modern cutting edge AAA games because of that would be absurd
In the same way black and white films are outdated, films with no cgi effects are outdated, but these do not diminish them, though if people dislike black and white films or flimsy special effects then its understandable they'd take less enjoyment out of those works
The Souls games are practically revered because of their outdated systems, how many other modern games send you back to start of the level if you die? That's very much a gaming convention that has all but left the current AAA sphere
This is where the line cuts for me:
Iterative succession
Serendipidous perfection
Aborted evolutionary lines
People who've changed
Iterative succession is where a game has largely been surpassed by its successors overall. Warcraft 1 vs Warcraft 2 was a good example; same aim, but 2 is bigger better and badder than 1 on most accounts. Legend of Grimrock 2 takes 1's formula and runs with it in a similarly successful drive forward. Street Fighter 2 blew 1's doors off to a near-infinite degree, and so on.
These are always a case of the latter being better. "Nostalgia" often doesn't really get used as a debate tactic, as few will argue the early ones are better than the latter.
Serendipitous perfection is games where everything just lines up, often at the end of alot of mechanical, narrative, and pacing tinkering over a period of time. Third Strike, Civ 4, SSB Melee, NHL 94. The lines of that subgenre of game continue on, but many argue that combination of goal and results haven't been surprassed by anyone attempting something in the ballpark since.
This gets the "Nostalgia" handwave quite a bit, especially by strident fans of later, quite good iterations. Apples and oranges. Much salt ensues.
Aborted evolutionary lines doesn't mean that no one does that kind of game any more, but it does at least mean that the GOALS of that genre have swung to far different directions. Wizardry games where the dungeon itself wears down on your reserves and not pacing for a boss...games like Souls, Unreal/Quake, and OG Tomb Raider that have very specific controls that demand strong understanding to play and mastery to win with, or MMOs where us the players are not required to win to enjoy themselves and cooperation and competition between individuals on a long-term basis is.
These are ground zero for "Nostalgia" bombs. Note also how much of this isn't in perfected later alternate, but of an easier, simpler later alternate...
And finally, some people just change. They don't understand those who like these classics; hell, they wouldn't even understand their old selves!
Again, much salt and argument.
What's really bad about this is it masks problems that need fixing iteratively and enshrines Player Bribery in its place in the queue to be fixed. Also does a real disservice to classics that have a few facets that iteratative change has fixed (System Shock 2), but the rest of the game is arguably head and shoulders above later games at those facets.