I've only beaten Blaster Master twice on the actual NES, any other time it was on an emulator with save states. If that game at LEAST had a password feature, I'd beat it all the time, but otherwise unless you plan to do an 8 hour expedition you can hang it up. BTW, I don't know if anyone else's cartridge was like this, but I remember a MAJOR glitch on Level 5 where if you were swimming in the wrong spot by a wall at one part the game would trap you into the wall and about 5 hours of gameplay was dead.
As for underappreciated NES classics I've played, let's see...
Chip'n Dale's Rescue Rangers:
Remember what licensed games used to be like, you know, back when good companies were actually doing them? 2 player simultaneous, quite a few stages which involved platform gameplay and throwing things at enemies, and not hard, but not braindead easy either. Rented it once and bought it soon after. This game was produced by Capcom, and I'm not certain on this, but I believe the game was led by Shinji Mikami. I remember someone saying that he used to do games like this.
Anticipation:
Really fun family game for what I believe to be 4 players. Everyone picked one board piece from a selection of eight, including a hat, ice cream, a teddy bear, high heel shoes, a tuba, and a few other things I can't remember at this moment. The board had 4 tiers and when you rolled the dice you landed on a color square which you would then try to figure out what the pencil was drawing. Each color represented a different theme. I remember the one theme that used to kill us a lot was "whatchamacallit" This game was produced by none other than RARE COIN IT, or as we know them, Rare.
"Oh what about Marble Madness, lol it's like the primal game-species of Super Monkey Ball. "
I had this game!!! Imagine if they could do a DS remake with a TON more stages.