I remember buying Super Mario Bros. 3 specifically. The excitement of the time made it one of those crystal-clear memories. £40 for that yellow box, a fortune to me but worth every penny. I played it all night every night until I completed it, to the exclusion of doing anything else.
SMB3 is such a perfectly crafted platform game, an art that's been all but lost in the rush and domination of 3D. Going back to it is a joy every time. The joy of perfect jumps, of precise and finely-honed controls, of pixellated characters full of charm and humour. It's a technical marvel for the NES, solidly outperforming pretty much anything else on the system, and it hasn't aged a single day (there are a couple of instances of flicker, but that's as bad as it gets).
The world maps, suits offering different abilities, and mini-games added another great dimension to the series, but in the end the greatness came down to the levels themselves. Designed to perfection and brimming with secrets. Gaming at it's most appealing.