Civilization series.

But I know that’s not what OP is asking for (but to be frank the question is too wide and unspecified).

For this thread I’ll go with Metroid and/or Kid Icarus on NES.

+1 to Final Fantasy 6. Great battle system, tons of content, extraordinary art and music, and some of the best storytelling and characterization in any RPG ever.

My short list would be:

1) Final Fantasy VI
2) The Legend of Zelda: A Link to the Past
3) Super Metroid

The 2D games that made the greatest impact were Pacman, the Super Mario Bros trilogy, the Sonic the Hedgehog trilogy, and the DKC trilogy. I’d probably toss Street Fighter 2 on that pile as well.

My personal preference would be Chrono Trigger
→ aesthetically, it had an impact similar to DKC for the RPG fan with the combination of Mitsuda’s scoring and the graphical direction of Tetsuya Takahashi including the translation of Akira Toriyama character designs to the game.
→ battle system is simple, and yet is equipped to handle complex situations including character placements, enemy and character co-operation, fields of effect, and background obstacles/barriers.
→ story, which was primarily written by Masato Kato and Takashi Tokita, with input from Yuji Hori and Yoshinori Kitase, had multiple routes and multiple possibilities, and was truly groundbreaking for its time.
→ It wasn’t afraid to leave questions open for the player to ponder (like the fate of Schala, will Magus search forever? - this is for the original SNES version; so, excluding the tacky DS additions from this calculation).
→ The 2D cinematics by Takashi Tokita and Yoshinori Kitase, and engineered by Tetsuya Takahashi’s team are outstanding, not just at its time, but to present day. These include the seamless transitions from map into battle, which is something that I believe is unrivalled in RPGs to this day.
→ The game broke a lot of the conventions of RPGs at the time, creating a much more cinematic gameplay experience which, years later, would become the norm in games like Tetsuya Takahashi’s own Xenoblade franchise and Yoshinori Kitase’s FF7 remake series (though, I have yet to play the later games)… But IMO, the 3D games have yet to match the tightness offered up by Chrono Trigger, even to this day. Or at least from what I have seen… they’re still improving; and it is interesting that over 30 years later the two major figures driving this are projects led by Chrono Trigger’s leading devs.

Anyway, that’s my personal vote:
Chrono Trigger

BRING IT BACK, SQUARE ENIX.... along with Terranigma and Xenogears.

I think it’s a good question. Basically, it’s just as valid as asking “What is the greatest game ever made?” but with the restriction to 2D. So no Ocarina of Time or Resident Evil 4.

Also, as far as my answer to this question is concerned… Yoshi’s Island (Super Mario World 2). You simply cannot compete with a game that has music this good (Athletic Theme, Course Clear Theme, etc.), with such creative ideas thrown every-which-way (2D platformer mixed with 2D shooter components, the creative damage mechanic of needing to recapture Baby Mario within 30s across a level, that one puff level, etc.), all while being the best looking 2D game produced prior to the N64 generation by a landslide margin. Easily among the greatest games ever made, far surpassing anything Mario World ever did IMO.

2D Sonic games (and Doom 1 and 2) are what got me into gaming as a kid. So I gotta go with Sonic 3 & Knuckles.

Civilization (1991) It was truly epic at the time spanning 3,000 years.

SMB 1 for innovation, because it basically invented the wheel. SMB 3 for everything else. Seriously. I could play that game right now and every day of my life and never get sick of it. It's the 2D game to end all 2D games for me.

Baldur's Gate 2. I had to replay the game a couple times due to different path and number of choices a player can make in the game.