Probably Combat for the Atari 2600. I probably played full size Arcade games before we had one of those but I don't remember them. Even at 34 (now) I was extremely young when the 2600 was in it's heyday.
As far as how the experience itself was, well I'm still a gamer today.
Honestly though I only became a "serious" gamer with the Commodore 64. Ultima, Might and Magic, Bard's Tale, Wasteland. Then we got like a Tandy 1000ex and there were things like King's Quest, Wizardry, and others.
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