Back then this was practically soft-core because there wasn't a console game at the time that even HINTED at the hero getting some action. It's insinuated that Duke and Cherry got their 8-Bit freak on and that was enough to make almost any early-pubescent boy giggle when the lights went out. And yes I was one of them, especially when Duke's life filled back up.
Back to the violent games-it's been a long time but I think Freedom Force was the first NES game I can recall seeing bone-fide blood. Granted it's not much-just a splotch on your target's chest, but it was an eye-opener back then.