I miss playing that on my NES (which almost never works anymore); however, I miss the original Legend of Zelda more. I played that game on and off for years and I think I still only am on the fifth labyrinth...
I saw a guidebook at a garage sale after I hadn't played for years, and I bought it, mostly as proof to myself that, yes, it can be beaten.
In SMB, I don't think I ever got out of the first castle, though, so I don't know how much can be said for that...