I just beat Castlevania for the first time last night on the Virtual Console
That game makes me angry
Another one I'm adding to my list is Kid Icarus. I can't believe that one hadn't occurred to me until just now.
Keep the suggestions coming, guys...I'll probably just stick with games I've played firsthand, and obviously you don't know what those games are, but some of these are sparking my memory.
Oh, and Contra is actually pretty damn hard if you don't use the cheat code.