Super Mario Bros 3 (no warps)

1991, Age 9, and again in 2002, Age 20

At this point in our lives, my friends and I had specific synapses in our brains devoted entirely to the play of Super Mario 3. But there was one other challenge we shared in common. Sure, we'd all play the usual way…get the whistles, warp, warp from the warp area, straight to world 8, right? But we had never played the game straight through with no warps.

It tooks us 2 days of swapping play turns, but we eventually saw every world the game had to offer, even that stupid hard one in level 5 that you can barely get past. It speaks of this game's awesomeness that it had enough stimulating content to drive us through many years after we'd all first played.