The trick here is that, unlike in the first two games, enemies do not respawn. So long as you're careful, take it slow, and take on enemies one at a time, it's a little easier.
I... didn't actually notice this. Wow. That's kinda cool, actually. Although I think it was always environmental hazards that tended to get me. Stupid spike traps.
Have you beat the Grim Reaper in japanese Castlevania III ? He's waaaay harder than in the US/EU Castlevania III.
Yeah, I beat the Grim Reaper in
CV3J. I didn't remember him being
that hard, but what do I know?

I'm not sure people would consider
Ninja Gaiden a piece of cake, even if it continued at the right point, but infinite continues certainly alleviate some of the frustration. The game is still tricky, and pure memorization and twitch memory is the only thing that will see you through. And it's not so much the
rate of respawns, it's where those respawns
occur. There's one jump in 6-1, in particular, that is tricky as all get-outs. Hawks that spawn while you're in mid-jump are
evil.
Battletoads is still crazy-hard. I know it's not impossible, but that Rat Race level is the one that generally takes me out. I also abuse the heck out of warp zones. There's very little to no margin for error in the game, so I suppose one could call it "easy" if you maintained perfect memory of what to do, maybe not unlike what I tend to do with
Contra. That's a game that I always expect on "hardest games of all-time" lists, yet find it rather easy. But then, I realize it's just because I've played it
so much. And it's pretty easy to say "just do what you see in the videos", but often times, it takes amazing skill to reproduce and execute on that plan. It reminds me of watching that first-round KO video of Tyson, thinking, wow, that looked easy... Psh. Yeah, right. It takes pitch-perfect timing.
I do have to admit that I've never sunk the kind of time into
Battletoads necessary to get that good at the game. I should probably try to do so sooner rather than later, before all my reflexes disappear in old age.

Anyway, I know everyone gripes about the Speeder Bike level in
Battletoads, but I also find that to be kinda easy.
EDIT: Plus, you can apparently cheapshot the
crap out of both incarnations of Death. The same can't be said for
Battletoads.