Mega Man 5. I used to confuse this game stuff with 4 because I could barely recall unique things from those two, unlike the other NES entries which have a stronger identity. Now I can remember 4 well, but most of it is because of Minus Infinity I think, and 5 still have some lacking for me, I believe it's the lack of innovation or new mechanics, besides a much better charged buster shot than the previous one. Played it again and still was the least memorable run for me so far, the same goes for its OST, which is just alright. But is not bad, it's just too average, a truly Megaman game for sure.