Obviously technology continues to improve video game graphics. I recently had opportunity to play the old school game Ultima IV. It strikes me that given the memory and technological constraints of the time, it is a perfect game. Great story, groundbreaking and widely copied characteristics, amazingly complex, both fun and surprisingly good graphics and sound.
(This must have been done before, but my search too is weak, and maybe not recently.)
But what is your equivalent?
Space Wars, mid-70s. One of the first, after Pong. Nothing beats it.
The Syphon Filter games on the PS1 were perhaps my favorite franchise that I’ve ever played. Close runner up, the original Sim City.
Super Mario Bros. 3 for the NES was an amazing game, but it was without save states in its original form, and is a looooong game.
Agreed.
Agreed. I have a t-shirt with the OG Sim City cover art on it the comments I get from millennials when I’m out running errands are legion.
My contribution: Heart of Africa for the Commodore 64.
Oh. And the original Tomb Raider. It’s now available as a digital download for the Switch and yes, I bought it on day 1.
Does Lord of the Rings Online count?!
It’s over 13 years old … but is still going. 
(The current plan is to move the Servers from 32 bit to 64 bit.)
I think a lot of the arcade games from the 80s and also Commodore 64 games hold up very well. They had little computing power to work with and therefore few opportunities to wow with graphics. So they had to design playable games.
On the Commodore 64 I’d venture to say I’m the best Dino Eggs player in the world. I’ve been playing it since I was 12 or so, and still do. Using an emulator, it can be played for free, offline, and without hassle. It’s still challenging, unforgiving and I can play while listening to podcasts.
I have a PacMan cocktail table with over 60 arcade games from the 70s and 80s. The only games I haven’t gotten sick of are Scramble and Phoenix.
I still have a lot of love for several arcade games from the '80s:
I was mostly into Punch Out!, Karate Champ, and Out Run. Those were my go-tos for the arcade.
For the NES, my big ones were:
On the C64, I spent a ton of time with:
Phantasy Star 3.
To clarify: the first Star Wars arcade game. 
It remains my favorite Mario game of all time and it’s still a blast to play. Asking me to narrow down my list of beloved retro games to one single favorite is a Sisyphean task I’m simply not up for. Back in 2017, I bought a Nintendo Switch and was able to play the original Legend of Zelda game for the first time in about 30 years. I still had fun with it.
I loved, loved, loved what I knew as Warsong.
I say that noone has the right to call themselves a “gamer” unless they’ve beaten Ultima IV as a shepherd.
For SNES:
The Legend of Zelda: A Link to the Past
Super Mario World
Super Mario All Stars
Super Mario Kart
Yoshi’s Island
Donkey Kong Country
Tenchu Stealth Assassins: I just like sneak-around-and-kill-people games with lots of gimmicks, and this was a big early one for me.
The original Armored Core trilogy.
SunDog: Frozen Legacy: The game was basically the embryonic version of space trading and simulation games. Trade between planets, drive around on planets, meet in bars for information and black market equipment, replace and repair damaged or less powerful components in your ship, etc; lots of stuff that’s familiar these days, just much simplified and with much more basic graphics.
Street Fighter II.
Blanka was one of my go to fighters, nothing was more satisfying than eating an opponents face then when they tried to attack you back you electricuted yourself… Between those 2 moves you could lock them up for a good 30 seconds…
Centipede. At the frat house we had an early arcade model with the big track ball. I wasn’t that good at it but I enjoyed it.
What I really liked about it was the way the colors on the screen changed with every level. The longer someone played, the more interesting color combinations appeared. I’d just stand behind a better player to watch the colors!
For best for its time, I’ll go with the OG Final Fantasy on the NES. It doesn’t hold up in its original form, but it was groundbreaking. For best for its time that also still holds up, even in its original form on SNES, I’ll go with Final Fantasy IV. It’s one of the best JRPGs, even when compared to current games. Honorable mention to Suikoden, which despite my avatar doesn’t compete with Final Fantasy IV.