Dungeon Keeper, Command & Conquer: Red Alert, Starcraft, Legend of Zelda: A link to the Past, Super Castlevania, Ninja Gaiden, SuperMetroid.

tons more I can't think of atm but there's a few.

I don't know if it's considered oldschool, but currently I'm completely hooked by Oldschool Runescape again, love the nostalgia, the music completely triggers monkey brain happiness responses :-D

I come to answer this and I am totally thinking we are talking about like board games. You know what people played before video games. I was thinking along the lines of Life or Mastermind or something like that. However since you seem to be talking about video games. I loved Mario 3. I also loved Marble Madness. 

I always loved point and click games, so Full Throttle, Escape from Monkey Island, Twinsen's Odyssey i liked a lot.

I also liked Quake, Doom and Duke Nukem

I generally like to bust out Mario Bros and Pac Man every so often and blow the rust off my skills.

I have an old school would I loved was Ghouls and Goblins. Never could get more then a few levels. 

A few that come to mind are...

DOOM
Quake
Duke Nukem
Tetris
Pac Man
Donkey Kong Country
Sonic The Hedgehog
Tomb Raider

Myst! I got stuck in one of the extra worlds and hit a wall. Downloaded the game on my phone 20 years later and realized it was a sound puzzle and my lack of speakers in the 90s was my wall. 

There were a few I particularly enjoyed back then; used to have a lot of the Need for Speed games, a Sonic game or so and then got hooked on oldschool Runescape, back when I was happy to get rune armor lol

used to love hexen on the ps1 kind of doom rip off solve puzzles kill mosters pretty cool...

but also knights of the old republic on origional xbox.

makes me sad that these games are now considered old... im not that old

favorite old school game is easily tony hawk on PS1.  N64 -> goldeneye takes the cake.  going back further, sega genesis NHL was the bomb.  SO many quality games back in the day.  For xbox halo original was the best.  I can go on and on

Does anyone remember the old school game called Neighbors From Hell, it had this artwork and the whole game looks like it was drawn but really nice coloring and it was amazing game because basically every level had like few different traps that you could do and your job was the kind of figure out what was his daily routine so you can like combo it and you also had to walk around the house not being caught and you would have to grab stuff that you would afterwards use for the pranking. An example you would take a glue from the garage and then you would put it on the toilet seat and then you would change the toilet paper with sandpaper and then you would put the firecracker and stuff like that but it was very important to make a big combo because that way you will get way more points and finish the level and it was really fun because it had a lot of different levels and it'll different traps and they had dog so it help to avoid them as well etc .so there's like a bunch of things that they added into the game and I think it was really amazing

Also I am using voice-to-text so if you find something weirds, don't blame me

I think a few that come to mind are definitely Street Fighter II championship edition, Sonic 2, Spider-Man Maximum Carnage and Fatal Fury 2. I played all of those games so much on my Sega genesis back in the day all the way up until we finally got a Playstation 2.

I always thought Go-fish was a pretty great game. Although as I got older I preferred spending my time playing spades or Egyptian rat-screw with my friends at the 24 hour diner because what the fuck else ya gonna do in a cornfield, ya know?

For me has to be Pokemon Yellow, Yes ive has the SNES and Mega Drive and so on, but my time spent playing Pokemon Yellow are some of my happiest memories, it kept my mind busy and made me feel 100 miles away from my bullies, even when in hospital recovering I was playing this game. I still have it and will never see it go.