If you could only own & play 1 single Famicom/NES game...

[Ghegs]

Tetris is a game with real unlimited replayability, but sadly none of the NES/FC versions are that great, at least not when compared to some of the later ones. So I'd probably have to go with Recca as well. The normal gameplay modes (both Normal and Hard difficulty) would be exhausted fairly quickly, but the Score Attack, Time Attack and Zanki modes would keep me busy for a loooooong time.

[L___E___T]

Rockman 1!

I can play this game over and over again. And why? Don't really know, I loved this game all my life, and it is quite a while. I know all the levels so good so I think I can draw them from memory And I love the music so I play it sometime just to listen to it for a while.
It's the legend that started the whole Rockman/Megaman madness!

I just downloaded it to my 3DS to play on my journeys, so yes, when I will be given the choice to keep only one of my carts, I have a clear winner. I also love the colour and artwork of the famicom cart!

You actually finished it??  I may go for it next after beating Castlevania, it's harder.

[Nightstar699]

I never understood why people claim the original Rockman to be a difficult game... I'd say it's just as easy as 2-6. Is it simply the lack of E-tanks?

[L___E___T]

The Wily Castle bosses for me - copy Rock and that eye/brain thing.

Most enemies also want to mate with you, the way they rush in relentlessly.

I think 2 is way easier than one for sure, even the Japanese version.

[crade]

Probably ghosts n goblins, it's the one that I have had the most fun with lately. 

[nerdynebraskan]

@nightstar

The Yellow Devil is very hard, and the final Wily boss is pretty tough too. Combine that with the lack of E-tanks (meaning you have to beat them with one tank of health), and the first Mega Man is very hard to beat without exploiting the pause glitch. The level design is also very tricky, and there's no momentary invincibility to save you from instant death on the spikes if you get knocked into a pit.

[son_ov_hades]

Super Mario Bros. 3, I've played it my whole life and haven't gotten bored of it yet so I doubt it will ever happen.

[Nightstar699]

Huh... I guess I just play way too much Rockman, because I found all the Wily bosses to be easymode. For the Yellow Devil I just memorized the pattern that his pieces fly at you, there's only one pattern and it stays consistent every time, from there he perishes after a few rounds of electricity. Rockclone, I just use Fire Storm, and it does a great job of keeping him at bay. I've also beaten him with the Buster, but it was tougher. For the large bubble-like monsters that move along the edge of the room, I just hammer away with the Buster, and use the boulders in the room to destroy the last few. As for Wily? Well, I found that Firestorm shreds through his first form extremely quickly, and I use Cutman's blades on his second form. It takes a while, but his shots are predictable enough that they're very easy to dodge.

[nerdynebraskan]

I've come to the same strategy and weapon selections on those bosses. I also find the Rock-clone to be pretty easy. He's a bastard if you don't use the fire, because he just jumps on you repeatedly, but that flame shield is something he just can't counter. I used to have a lot of trouble with the bubble things as I played it growing up, but they're really not bad if you keep the boulders for a platform to jump over them when they rush you. It was just always tempting to smash them with Guts Man's power immediately or to zap them with Elec Beams (which destroy the boulders). If you make those mistakes, the last couple will often kill you because you can't jump over them.

As much as I agree with your assessment of Yellow Devil, he's still the hardest boss in the classic series. Yes, he's predictable, but he's fast and your window to counter-attack him closes very fast. Without exploiting the pause glitch, you have to survive his barrage, what, six or seven times? That's not easy for most of us. And the final Wily boss is still an endurance, because he has double your life bar and does more damage than you do.

The first Mega Man is still a tough game for me. And I'm someone who's beaten Mega Man 2 and possibly 3 without using special weapons (as much as possible... obviously late bosses in both games are immune to the pea shooter).

[aha2940]

I would have to say Akumajou Densetsu (Japanese Castlevania III). It has all the things I like: lots of challenge, great graphics, great music, replayability value (multiple paths). Great game and maybe the best one for the NES IMO.

Regards.

[zaneiken]

Double Dragon II - still fun after all these years.

[Farid]

With no doubt it is : Kunio-kun no Nekketsu Soccer League

This game has changed my life and still it is changing it! 

One day I will go to Japan and talk to its maker personally. 

Also there are other reasons :
There are a lot of humor in it which make me laugh while playing
It has a 4-Player support and because of this I still play this game with my cousins whenever possible
I remember I became angry at my brother for buying this game!
Because I am not a soccer fun so at first I didn't like this game at all but gradually I fall in love with this SUPER GAME!

[egg_sanwich]

Gradius. It's not rare, it's not top 10, but I love it! It boots up every time I plop it in, and boom - instant shooter action.

[That Guy from Faxanadu]

I´d choose Quarth. Best puzzle game for any console. I never get tired of it 

[sconley666]

The Wily Castle bosses for me - copy Rock and that eye/brain thing.

Most enemies also want to mate with you, the way they rush in relentlessly.

I think 2 is way easier than one for sure, even the Japanese version.

2 is WAY easier.  I personally thought that 5 was the hardest, with 4 being a close runner up.  1 2 & 3 are the easiest but they also were the only ones I had for quite some time.

One 1 game?  I have a hard time with this.  Either Mario 3 or Tetris 2 + Bombliss I can't decide.