I choose games that I like and that shaped my taste. Could pretty easily also choose games I did not like that shaped me as well. Some like Fire Emblem Sacred stones and Zelda BotW probably shaped my taste more then a few of the games i picked, because i did not like them. 

Was hard to keep it to just 9!

Other titles would be SSX Tricky, RuneScape, Minecraft, Terraria, Rollercoaster Tycoon, Empire Earth, Wipeout Fusion, LittleBigPlanet, Animal Crossing Wild World...

Building and exploring are my drive in gaming. FPS and RPG I mainly enjoy the exploration, combat has always been the hurdle rather than the goal. I was into competitive shooters in LAN for a while and still am into racing as well. But also with racing I'm more into the track (exploration / experience) than competition. I always enjoyed racing with weather / day-night cycle, long tracks, rally in nature. Nascar being the least fun.

I started with building type games, Civilization, Railroad Tycoon, Sim city consumed most my time in my teens.
Special memories of Everquest where I met my wife, moved in together to play alongside, then continue with The Sims (2) where we build our virtual life together while play WoW alongside. ICO has a special place as we played that together when she came over to visit and left it midway until I emigrated where we picked it back up to finish.

Flight simulator has always been with me and with 2004 I started exploring the world which evolved into my biggest gaming project ever in FS2020
https://forums.flightsimulator.com/t/exploring-the-world-in-the-beechcraft-bonanza/266981

Which reminded me of space exploration, which got going with Frontier Elite 2 which we played at university in the computer lab after dinner in the mensa. And resulted into the second biggest gaming project which I recently restored (links and pictures)
https://forums.frontier.co.uk/threads/exploration-quest-for-the-loneliest-planet.132053

Currently going back to basics, playing Dorf Romantik.

I played Elite on C64 and that was for me mindblowing experience (apart for pen&paper D&D, that's probably the game that most influenced my gaming taste). It didn't run half bad either...well for that era. I had Frontier first on Amiga 500...that was quite a slide show...only later I've played it on PC, where it ran smoothly, but by that time First Encounters (Elite 3) already came out ('95) and my focus was almost solely on that one.

Elite Dangerous has been patiently sitting in my library for so long...never touched it...I know I would have to say goodbye to my dear ones for at least a month, which is not an option. My younger son have shown interest in it (via Quest 2), so I guess at least it stays in the family.

From chronological order, these were the games that impacted me the most, that shaped my gaming tast and/or that I spent years playing majority only them. It's a shame I dont have one more space to include Crash Team Racing, though

Only the 9th choice was sort of tough

Had a hard time deciding on nine games, but these are the games that I think have shaped my tastes as a gamer the most up to this point in time, not the games I consider the best I've ever played, though there's certainly some overlap. Many are from my childhood from the 90s and early 2000s, but there are a few much later titles in there as well.

Pretty hard to reduce it to just 9 games, at least for me, so I made 2: The 9 games who did and those who are the runner-ups who also did shape my gaming:

Runner-ups:

And this is still missing some games, like Tetris, Lemmings, Wolfenstein 3D, Mario Kart: Double Dash, Heroes of Might & Magic III or Monkey Island II: LeChuck's Revenge or Unreal Tournament, but I had to cut this off at some point...

You might already have run into this a bit, but just you wait until you get to the point where you see things and realize how old they are, then realize how old you are - and let me tell you, it doesn't get any better, it gets only worse the older you get. Enjoy being young while you still can.