Many games have a pure nostalgic value, but are rarely fun to play. But there are games that still holds up extremely well against modern titles. Castlevania Symphony of the Night, Super Metroid, Final Fantasy 7, R-type, Wipeout 2097, Wonder Boy III, all are amazing games that are fun to play even 20-30 years later.
I'd argue that they don't necessarily "hold up" against modern titles, so much as they were so well designed with their technical and mechanical limitations in mind, that technological progress and progress of modern games didn't manage to add much to their formula. Similar to how chess exist as a timeless game that wouldn't necessarily benefit from adding e.g. "line of sight" mechanics or football is played largely the same way as 70 years ago and adding more players per team and three differently colored balls wouldn't necesarily improve it.
I'm thinking especially about things like FF6/7/..., Super Metroid or Zelda AlttP. You do not necessarily care (as much) that they're technically behind something like RDR2 by about 25+ years, because their design is so well made from a mechanics and game design perspective, that the technical limitations become a bit of a non-factor. If a modern game picks up and variegates the same formula with relatively little changes, e.g. Hollow Knight (most highly recommended for Metroidvania lovers) compared to Super Metroid, the fact that the game's formula is essentially 25 years old, doesn't hurt the experience much.
But compare early, clunky 3D 3rd person action platformers with a bit of shooting to modern entries (old vs. new Tomb Raider) and you may realize that the game's mechanics benefitted immensely from technical adancements and the old games properly feel old and outdated.
Which is my problem with the early 3D systems, like the PS1 or N64. Even of my favorite games from that generation, Zelda OoT and MM, I'd rather play the 3DS ports, which don't run at +/-20fps but at a solid 30fps and sport some carefully polished visuals.