I'm old enough to remember Super Mario Bros. when it was a new game. I remember seeing it for the first time back in like '87 or early '88 when the NES really started to get popular, and I thought it was the coolest thing I had ever seen at the time.
Every other console game from prior generations were not only more primitive technically, but also in terms of gameplay. Not only did Mario look more like an actual human being instead of a nondescript assembly of rectangles approximating a humanoid shape, but the scrolling screen was something new to me, and the whole gameplay experience was more dynamic and involved than the simplistic arcade action of the Intellivision games I played beforehand, where there was no real ending and the only goal was to rack up as high of a score as possible. But Super Mario Bros. felt like a real adventure. It had all these unique, discrete levels, and an actual ending.
Super Mario Bros., and the NES's library in general, was such a massive evolution from the gaming experiences of the early 80s, leaving behind many of the limited design sensibilities of the Golden Age of Arcade Games that informed console game design in the pre-Crash of '83 era.