Double Dragon was a huge hit back in the day, and for the strangest version the NES Double Dragon is one of the most played and remembered.
Not to say the arcade version wasn't a hit. I'm sad to see them take it off XBLA due to copyright concerns when a company folded.
The NES version took a huge hit in graphics, and there was no Co-op. More like single dragon if you ask me. But it does have a bit of it's own style and it's a bit unique compared to the other DD ports. There was even a decent vs. mode.