Double Dragon was definitely "cool" back in the day. But my memory says that I didn't really care all that much about the series until Double Dragon II came along and added co-op to the mix. I'll be honest - and this might be a crazy thing to say - but as far as single player NES beat-em-ups go, I vastly preferred Renegade.
Of course I didn't know at the time that the two games were kinda sorta related. Renegade was a localized version of the first Kunio-kun game. I think it was the first. I'm not gonna Google it. And then Double Dragon was sort of a spin-off or spiritual sequel or whatever. But the two series have always been a bit intermingled over the years.
Renegade was awesome, though. It had such a great environment. The subway station platform and the burger joint and everything. It was so cool. Double Dragon is cool, too but it feels a bit less diverse. A little less inventive.
Don't get me wrong - the factory area where you can knock dudes onto a conveyor belt so they fall to their deaths? That's awesome. And there's some interesting enemies like Abobobo of course. And y'know, enemies get harder and learn new moves and so do you. It's good and all. I just think I got into it at the wrong time. Like, I already played and loved Renegade. And not long after this, we'd see the release of Double Dragon II and play it with friends and the original game was rendered obsolete.
I do remember playing the GBA remake later and thinking it was impressive. But I don't know. Double Dragon is fine. It's good. I like it. Just not as much as its sequel, nor the myriad Kunio-kun games out there.