Double Dragon is another of those classic coin-op games for which I own the original board (I also have the Double Dragon II board). For comparison's sake, you may like to browse my page describing the Japan Technos coin-op, on which you can view screenshots and download RealAudio clips of the in-game music, which is very good. In fact, the music from the coin-op was so good that Your Sinclair magazine published it on a "classic arcade game music" covertape in 1990 or thereabouts.
How does the ST version rate? First, let me give you a little diverting information on the man who converted it to the ST and Amiga, Richard Aplin. He also did the Amiga and ST conversions of Double Dragon II and, later, two Capcom CPS-based coin-op games; Line of Fire (similar to Operation Wolf) and Final Fight (a much more impressive side-scrolling beat'em up). Although I don't recall specifically, he may also have converted Ghouls'N'Ghosts (another game which runs on the Capcom CPS1 coin-op hardware). Richard was given to putting long personal texts somewhere on the game disk, for crackers to read. The text buried on the Amiga version of Line of Fire, for instance, talked a little about the Amiga crack of Double Dragon II - it mentioned the cracker (Weetibix) by name, albeit misspelled as "Weetabix".
Anyway, Final Fight was a superb conversion, as was Line of Fire. Double Dragon II was mediocre. Double Dragon is awful. I've played the ZX Spectrum, Commodore 64/128, Amstrad CPC, Amiga and Atari ST versions of this game, and all of them have unforgivable faults. The faults you will notice in the ST version are a shortage of frames in the sprite animations, a small play area, utterly silly spot effects (Richard, did you sample your own voice for those?), and the cardinal sin - excessively easy gameplay. If you sit down and play this game, you will be able to complete it on your first try, which for £24.99 (the original retail price) is extremely poor value.
The game does have a couple of upsides - the first is that the title screen plays a rather good sampled version of the music from level one of the coin-op. The second upside is that the overall graphical quality (leaving the poor animation to one side) is quite good, though I believe it could have been done better. It's worth getting this game as a part of history, but not much else.
Verdict: Not a very good conversion, far too easy to be interesting, and poorly animated. The ST is capable of much more. The sound score is high because of the good sampled title music, not the silly in-game sound effects - if the home computer programmers had the coin-op board handy to sample out the title music, why did they insist on using their own silly samples for the various screams and grunts in the game?