Seriously?! You BEAT Battletoads? On NES? Dude, that's "we're not worthy" bragging rights! I could never get past the hoverbike level. Most of my friends all say, "Dude, none of us got past the hoverbike level." And, as an aside, I'm sure several folks had pixel crushes on Dark Queen. For the heck of it, I watched the final battle and ending on YouTube and LOL'd when
Dark Queen called them Cattle Loads.
Yeah, that's pretty impressive, Ramza. I too never made it past the hover bike level.
A few games come to mind:
Original NES TMNT - I could usually do pretty well until the last area when every enemy was essentially a boss. Shredder destroyed me a few times before I beat him, and I didn't even know about the cheat back then!
Gargoyle's Quest 2 - It's not as hard as Demon's Crest (never finished that one with the best ending), but it was still pretty difficult. Part of that difficulty came from the slowdown that occurred when a lot was happening onscreen. It was all kind of exacerbated by the fact that there were a couple of times I had made a mistake when writing the passwords down and had to go back to the previous password and play through a level again.
Mega Man - I actually find the first game in the series to be the hardest. Especially once you get to Wily's castle and have to face Yellow Devil, and the crazy level where you have to use the Magnet Beam. Like the TMNT game, I didn't learn of the pause trick with Elec Man's weapon until later.
Adventure of Link - It seriously took me close to ten years to finish it. I will never play it through to completion again.
That's all that come to mind.