Hooked up my SNES last weekend and played Chrono Trigger for the first time in like 10 years. Game still holds up better than 90% of what came out this year.
There's something about 16-bit games that modern stuff can't replicate. No 40-minute tutorials, no login screens, no battle passes. You press start and you're playing. The respect for the player's time is something the industry completely lost.
The sprite art aged way better than early 3D too. Go look at a PS1 game and compare it to Super Mario World. The SNES game looks timeless and the PS1 game looks like a tech demo gone wrong.
My top 5 that are still worth playing right now: Chrono Trigger, Link to the Past, Super Metroid, Final Fantasy VI, and Streets of Rage 2. Every single one of these is better designed than most $70 games on the shelf today.
If you have kids, honestly start them on the classics. My nephew went from "these graphics suck" to being completely addicted to Mega Man X in about 15 minutes. Good gameplay is good gameplay regardless of when it was made.