I played part of...Dual Strike, was it? But then I immediately went to the darker one. Not because it's so much more difficult (and dear Christ was it, never got too far into DS so I can't say for sure, though), but I liked the anime style mixed with a Western aesthetic, creating a wider appeal than "just anime" or "just cartoony" would, and I think that was a smart idea.
I'll probably play the others eventually, but I certainly like what they did with that one. I pretty much avoided DS because I assumed it was going to have simple characters, a simple story, and just gameplay to hold it up, as was evidenced by the dialogue. Maybe it wasn't that, and it's been a while since I played DS so I can't say for sure (It could've easily been a misconception, this was years ago and it was when I had a crapton of roms on my cart at the time, so it's likely), but I dug the feel of Days of Ruin. Other than the aesthetic, I thought it handled the shift to a darker setting nicely. It was gritty, but not gratuitously so. Everyone wasn't mad all the time and always talking about how bad things were, and people smiled. And the story had a mystery to it. It was so open that you could never really know where it was going to go next, and that was really what drove me to beat each level in that horribly...horribly...HORRIBLY punishing game. Haven't beaten it solely for that reason. It hurts.
...Though I don't think that they should dwell in the darker setting. It wouldn't work well a second time, and it could EASILY fall into the realms of the generic really quickly, and that kind of takes away any part of what makes Days of Ruin unique and...well...good. They can hark back to the days of Famicom Wars or create a new universe for all I care, just don't milk it for what it was, 'cause it'll spoil real quick.
I'll revisit DS and the GBA ones, of course. It's not like I don't like the games, after all; I've barely played them.