My first console was the NES (No I'm not 50, it was my dad's) so I have a lot of nostalgia for it, particularly for a few games I played a lot.
-Dragon Warrior 1: When I was 10 I somehow managed to actually beat it. Took me a really long time though. Definitely wouldn't have the patience for it today.
-Zelda 1: I also managed to get to the last dungeon in this one, just based off of tips from my brother. Then the cartridge wiped my save. Still mad about that.
-Kirby's Adventure: Didn't get this one until much later, but it's just so charming and fun.
-Startropics II: Along with the first, which I got a couple years ago, is one of the best games on the system imo. The gameplay is fantastic and both games have good difficulty; challenging but not impossible. The music is also great.
System Shock 2 is probably my favorite game ever. Beyond that, most of my favorites games were made in the 2000s so I dunno if they fit here: Metal Gear Solid 2 and 3, LoZ Twilight Princess, Mario Galaxy, and Star Wars Battlefront 2 (2005) to name some.
I also do really love 5th gen consoles like the PSX and N64; something about their visuals I really like. The original Silent Hill is one of the coolest-looking games ever.