Doom.
It was the first 3(well, 2.5)D shooter. Plus, I can hear E1M1.
And using the shareware license for distribution widely helped it’s popularity and it had multiplayer.
Honorary mention to Carrier Command ( the first one with like a 5 polygon island and a 40 polygon volcano).
“We choose to go to the moon” was the first thing that popped into my mind.
And related to OPs quote. “If you love your job, you’ll never work a day in your life”.