What are your thoughts on the best "old school" video game?

Battlezone
Missile Command

One nice afternoon I decided to visit my brother and his family.
He put in the original Mario on the 8 bit system and told me to try it. I explained that I was not good at those games with everything running around and hopping and jumping.
So he put in The Legend of Zelda....
That was my downfall :) After driving home (he lives in upstate NY, and I closer to the city)
Next day, I got out of bed and went to Toys R Us. Got the unit with the front flap that you lift and popped in the Legend of Zelda.
At age 75 I'm still playing Zelda and anything else that does not have sprites jumping all over the place.
I now have a PS4 and the Nintendo Switch. God help me :( I'm 75 and still get pissed my guy dies :(

Turtles in Time... has to be one of the best games of that generation. It surprisingly still holds up well today. Going back to the NES, I always loved Zelda, and Batman was a surprisingly good licensed game.

Tetris. I have two original Game Boys and the cable to link'em together to play Tetris against a partner. Last played it with my 9-year-old nephew (has a newer X-Box at home) and while he thought them odd, enjoyed it.

All-time favorite pre-2000 video game has to be the original Metroid on the NES. The soundtrack was hauntingly perfect. I loved the exploration. The majority of the game was trial and error. There was no map. I remember after getting lost the first dozen times to start mapping things out. Discovering power-ups that were just out of reach until later on kept you exploring the same areas multiple times to try different solutions. It was such a fun game that I've kept coming back to the Metroid series with each new entry and have rarely been disappointed.

https://en.wikipedia.org/wiki/Pitfall_II:_Lost_Caverns

Definitely wins my vote. I remember this game being sold out everywhere. I would borrow this cartridge from a neighbor and would play it for hours. I did not get my own copy until I saw one on eBay in 2003. I quickly registered for an eBay account and a few days later was in heaven.

I have too many to count... I practically lived in the old video game arcades! I have played everything from Pong to Star Wars. My personal favorite (besides Final Fantasy) is Donkey Kong Jr. from the Game and Watch Series.

If it's any system, to include PC, then I would definitely have to say Starcraft: Brood War. Best RTS ever made, and the game the evolved eSports into what it is today.

For Gameboy : Tetris, WCW: Main Event, Super Mario Land, and Metroid

In the Arcade : X-Men Arcade Game, Lethal Enforcers, Alien Vs Predator, X-Men: Children of the Atom, Area 51, and Primal Rage

For SNES : Super Street Fighter 2: Turbo, Mortal Kombat 2, Killer Instinct, Donkey Kong Country trilogy, Starfox, TMNT: Turtles in Time, NBA Jam, and TMNT: Tournament Fighters

For Sega Genesis : Streets of Rage trilogy and Mortal Kombat

For PS1 : Metal Gear Solid, WWF: Warzone, Tekken 3, Street Fighter: Alpha, Twisted Metal, Tony Hawk's Pro Skater, Rival Schools United by Fate, Street Fighter EX Plus, and Die Hard Trilogy

Hmm...Pre-2000? Pretty sure my favorite of all time was Zelda: Ocarina of Time. Before that, it was TMNT IV: Turtles in Time.

Before that, Super Mario Kart, and then it was Triple Action on the Mattel Electronics Intellivision II.

PC is a completely different animal though. The first Half Life Came out pre-2000 as well :)