I probably prefered Amiga DD2 to arcade version. It does play a little dfferent, but thats exactly why I preferred it..... no.2 was basically the same as no.1 with some different graphics in the arcades. Amiga DD2 was simultaneously both very double dragon-ish, and different enough from arcade DD1 to not feel like you was playing no.1 with different graphics. The gameplay in my opnion works quite well with the maps and enemies (plus their placement). Id even go so far as to say Amiga DD2 was more playable than arcade version (although arcade DD1 in my opinion was better than either).
No.3 was a great conversion (Sales Curve conversions were usually pretty good), and enjoyable enough, but I prefered no.2.
Slight sidebar, but DD3 is the only game I know of where you had to spend real money to buy upgrades in the games shops. Even as a big arcade game fan at the time I remember thinking it was a terrible idea. I wonder how much that influenced the games lack of success.