Double Dragon just hasn't aged well for me because there is so many beat em ups that came afterwards that perfected the formula they started. Its the perfect example of a game's history being more important than the game itself.
Having said that though, I used to play the Sega Master System version with my friends all the time when I was young and at the time I probably thought it was the best 2 player game ever.
Its still great to go back to that version and the NES versions based on the nostalgia associated with it, but I would understand if someone playing it for the first time today thought it was kinda crappy.