If we're picking a Game of the Decade based on which title had the most cultural impact, I think the only honest answer is the original Super Mario Bros. Wouldn't have been a Super Mario Bros. 3 (the candidate currently leading in our poll) without it, and for that matter console gaming itself may never have recovered from the doldrums of the early '80s either for that matter without it. It also sold more than twice as many copies as Super Mario Bros. 3.
But if instead we're just picking our favorite game from the '80s -- which is what it looks like people are actually doing (i.e. picking Super Mario Bros. 3 because it was more fun to play) -- then in that case I have a definite three '80s faves. They are:
1) The Guardian Legend
2) A Mind Forever Voyaging
3) Leather Goddesses of Phobos
None are nominated and there is no "other" option in this poll.