I honest-to-god thought it was one of the easiest "classic" 8-bit games out there. I can't get to world 5 in any of the older Super Mario Bros. games, Legend of Zelda 1 and 2 is right out, but I beat Megaman 2 in some short timespan, maybe two-ish hours.
I'm nowhere near a pro at the game series either. I didn't beat it taking no damage, using nothing but the arm cannon, with the controller upside down, on camera to raise money for cancer. I just played it, found the jumping and shooting controls to be real solid, and went from there. It was fun.