Are we supposed to be voting as though we're casting this vote in 1981, or are we casting our vote in 2023?
I think if I were voting in 1981, I have to go with Ms. Pac-Man. That game was a mega hit, and a good evolution on a prior mega hit. It's significance was much greater than the other games in that year.
But, as 42 years have passed since then, I can recognize that other games had a more significant legacy. I'd say donkey Kong is probably the winner, because of the Donkey Kong and Mario characters that came out of it. Others have already done a good job of mentioning the influence that many of those other titles had on future games, and still have today. Ms Pac-Man did not, I think, do as much to influence gaming down the road.