Castlevania 3 was my vote, but SimCity is realistically tied, and there are others that are very close from this year.

While some people see Symphony of the Night as Castlevania’s central game, for me it’s Castlevania 3: Dracula’s Curse. For those not familiar, it was a game with a branching story and levels. Playing Grant felt like cheating because of his climbing ability. But basically, you can switch at various points from Trevor (the vampire Hunter) to Sypha, Grant, and Alucard.
The original Netflix Castlevania TV series is based on Castlevania 3 - and unlike the vast majority of Netflix shows, this story actually finished.

Got to go with Final Fight is still one of the best beat-'en-up games of all time. Plus, the game inspired another great franchise in the genre Streets of Rage. Also, when it comes to SimCity the SNES version comes to mind first before the PC version or any other port.

Sim city actually has quite an interesting history, quoting from Wikipedia

The first version of the game was developed for the Commodore 64 in 1985; it was not published for another four years.^[15] The original working title of SimCity was Micropolis.^[16] The game was unusual in that it could neither be won or lost; as a result, game publishers did not believe it was possible to market and sell such a game successfully. Broderbund declined to publish the title when Wright proposed it, and he pitched it to a range of major game publishers without success. Finally, Braun, founder of the tiny software company Maxis, agreed to publish SimCity as one of two initial games for the company.^[8]

Wright and Braun returned to Broderbund to formally clear the rights to the game in 1988, when SimCity was near completion. After Broderbund executives Gary Carlston and Don Daglow saw SimCity, they signed Maxis to a distribution deal for both of its initial games. With that, four years after initial development, SimCity was released for the Amiga and Macintosh platforms, followed by the IBM PC and Commodore 64 later in 1989.<sup>[15]

After the original release on the Amiga and Macintosh, the game was released on the Commodore 64 and IBM PC compatibles, and afterward saw more releases for computers and video game consoles: Atari ST, Acorn Archimedes, Amstrad CPC, ZX Spectrum, BBC Micro, Acorn Electron, Super Nintendo Entertainment System, EPOC32, mobile phone, Internet, Windows, FM-Towns, OLPC XO-1 and News HyperLook on Sun Unix. The game is available as a multiplayer version for X11 Tcl/Tk on various Unix, Linux, DESQview and OS/2 operating systems.


The SNES version didn't arrive until 1991:</sup>

SimCity for the SNES features the same gameplay and scenario features; however, since it was developed and published by Nintendo, the company incorporated their own ideas. Instead of the Godzilla monster disaster, Bowser of the Super Mario series becomes the attacking monster, and once the city reaches a landmark 500,000 populace, the player receives a Mario statue that can be placed in the city. The SNES port also features special buildings the player may receive as rewards, such as casinos, large parks, amusement parks, and expo centers; some of which would be incorporated into SimCity 2000. A bank can be built which will allow a loan of $10,000 to be taken, but it must be paid back before another loan can be taken out. The game includes schools and hospitals, though they cannot be placed by the player; instead, the game will sometimes turn an empty residential lot into one. There are city classifications, such as becoming a metropolis of 100,000 people. It has some of the same pre-set scenarios in the PC and Mac versions and two new ones. One is in Las Vegas under attack by aliens and another is called Freeland. Freeland has no water, and no rewards for buildings are given. Also unique to the SNES version is a character named "Dr. Wright" (whose physical appearance is based on Will Wright) who acts as an adviser to the player. The soundtrack was composed by Soyo Oka. The edition is featured as Nintendo's Player's Choice as a million-seller.

In August 1996, a version of the game entitled BS SimCity Machizukuri Taikai was broadcast to Japanese players via the Super Famicom's Satellaview subsystem. Later, a sequel titled SimCity 64 was released for the 64DD, the Japan-only Nintendo 64 add-on.

Just wanted to mention Tecmo Bowl (1989) game. Despite I loved DuckTales, both TMNTs, SML soo much, I played Tecmo Bowl by far the most. Back in the days it was so enjoyable)

Put me down in the voting for Mother/EarthBound Beginnings as well. 

And just for fun...

Super Mario Land is my runner-up and I think it's the only other 1989 game I played through.

TMNT was my jam.

Another game I though launched much later, Indianapolis 500

This game ran so smooth on PC it felt like magic. It was pretty hard as well, and the best way to win was to turn around, crash the whole field and be the lone survivor lol. The crashes were epic :)

The racing game I missed from this year (because I actually thought it was older than that) was Super Off Road. But turns out the Arcade version also only released in 1989.

Pure mayhem and fun, especially with 4 players on the NES

Dang was that also '89. I played that so much on PC together behind he keyboard. Very fun addictive game, boosting around the tracks. The precursor to Motorstorm! And so evil, boosting players off track to miss a cone and have to turn back lol.

I've never been a pc player, but I remember hanging out at my neighbors house as a kid and watching him play Secret of Monkey Island and finding that final boss fight both hilarious and cool.  It was a bummer it never came to the nes/snes like Maniac Mansion did which I rate very highly.