If There's One Game Which Makes the Master System Worth Owning...
This is the best looking and most loyal port of the original Double Dragon. The Master System version fills in every aspect which its (rather illogically designed) NES counterpart failed to deliver: most significantly, a simultaneous 2-player mode. It was because of this game, the word "simultaneous" was burned into my vocabulary as a second grader.
The action is very similar to the very popular NES port, but the controls feel much more free-form, the sprites were bigger, brighter and everything ran smoother. I'm sorry to have to put it into as many words, but the only way I can describe the differences is that "it had a more Master System feeling to it" (I know, I'm lame). In addition, the 2-player mode was a much appreciated feature for anyone who desired a port worth of the arcade version.
Expect to fight your through the same rogue gallery (Williams, Ropers, Lindas, Chins, Abobos, etc.), and through the same levels (the alleys, the forest, bad guy HQ, etc.) with your full arsenal of moves is readily available; there are no hearts to accrue, and the points are there solely to engage in the videogame pissing contest that usually occurs whenever two grade school boys play together.
There is also a lot of fighting done on platforms, fire escapes and rooftops; these environments contribute to the feeling that you are chasing thugs half the time while being chased by the thugs the other half of the time. In short: being able to climb is good
Not to knock it, but you had to own a Master System to play it. To my knowledge, very few people owned a Master System compared to the numbers NES-nation had. Also, the Master System controllers were very prone to dig into your skin, and rather ironically, cause a nasty case of Nintendo-thumb. It's not Technos' fault that the Master System controller was designed by the Marque de Sade.
Also, this version of the Double Dragon is relentlessly unforgiving. It's very hard to recover whenever you lose a life; making it past the boss without dying becomes a crucial affair of life or death for the rest of the game. I found it literally impossible to complete the game without a partner.
The Bottom Line
This overlooked and relatively obscure console port is the best home version of Double Dragon series. It's surpassed only by the Double Dragon II NES port which is actually an unfair comparison since DBII for NES was completely redone specifically for the console.