None of them are that good.
Dynamite Dux is way too slow to be any enjoyable (It's shameful that the Master System version of this trumps all over the Amiga one). And the arcade game wasn't all that hot for starters either.
And Motorhead.... it had potential to be a lot better. I'll give in and say the game is indeed underrated and it deserved to be better known.
But the game does have a fair amount of serious flaws.
The enemies are incredibly repetitive in their attack designs. While it's cool to have a nice variety of graphic styles for them, the fact they basically all attack you the same way makes the game *very* repetitive very fast. (And it doesn't help at all that each level has a very limited set of enemies, even if they change every level). The lack of end-of-level bosses is a big letdown too. I like the bonus levels between rounds, *those* have some kind of variety to them, but I guess they added that exactly because the main gameplay is repetitive as hell.
I love the fact you have lots of different special attacks on the game, but as you use them over and over on enemies that are all basically the same makes this rather pointless.
And, of course, also lack of 2 players mode, which is the best way to play those kinds of games.
But they could have done a lot worse. They could have done Last Action Hero bad, for example (That game really get me on nerves, with just a few tweaks and polishing-up that could had been done in 2-4 weeks of extra work, that game could really had been *the* killer beat'em up on Amiga, or at least a kinda good one. In the end it became just an awful game that got ridiculous low reviews on magazines. It's not even as bad as the console renditions of the movie tie-in