The NES library had a wide variety of games to suit every tastes, It was here, that many big name game franchises got their start.
Mega Man was released by Capcom in 1987. It was the start of a major franchise. It was a game that decided to throw the linear concept in the bin and give players 6 distinct levels to play through.
Mega Man could choose any one of the 6 stages to begin from and play through the level to the end, where Mega Man would fight a robot master and gain their weapon to use in another level. The idea was to play the levels in a particular order to get all the secrets and weapons, plus use the correct weakness on the right boss. Getting it right, in this NES Hard game is what earned it the replay value.