I have the MVS version of DD and I will try and give you a little feel for it. The graphics are on par with Street Fighter 2, probably championship edition or so era. A bit dated, but I must say that it plays pretty well. The backgrounds are colorful and usually change through the board (The subway scene is pretty cool, doing a big combo can make stuff fall through the ceiling from the street above) and there is lots of things to break (the arcade). The combos are very SF2ish, but what isn't these days. One thing to note, this game is based on the Double Dragon Movie, and not the Game per say, so you have some contenders in here you may not be familiar with. Also, there is some FMV from the movie played at times which is impressive if you think of what it is playing on... but in all honesty it looks worse then SegaCD video. So, I would say... $50 max on this one for the MVS... home cart users, god I have no idea how much this would cost, but I am sure it will be too much. This is a fun one if you can get it cheap (mine was free, so I may be nicer to it then others), but it is pretty old, and is really pale in comparison to Waku Waku 7 or any of the other older SF2 style games on the Neo.
-Nick