I hate to join the doom and gloom crowd, but I think it's time for a sitdown. You might even want to do it via email, which has some pro's and con's.
Here's what I'd say, something to the effect of guys, there are, broadly-speaking, two kinds of games going on here. One of them is a chance to blow off steam and inflict massive mayhem, slaughtering everything in your path and so on. The other is a more story and character-driven game where the PCs are heroes and, more importantly, the DM has to take into account their motivations and personalities in constructing the story and, as part of that, the encounters.
Now, it sounds like you've been wanting to DM the second type of game, but some of the players, in various combinations, have been pushing for the first type. You may or may not be willing to run the first type -- that's your call. But, your intention is to run the second type. And, for that to work, they need to be on board with it. You don't want to be restrictive, nor do you want to tell them how to play their characters. But, in constructing the story and the campaign, to the extent it is going to have little things like plots, characters, and development, you need to be able to wrap your mind around their characters -- their motivations and so on. And, as of late, you have not been able to do that.
I'd present it to them like that and see what they have to say. It may be the case that things have gotten bent too far out of whack for them to easily get back into a more story-driven groove. And, I think ultimately, that's what the OP is aiming for. It's not so much a question good v. evil, but of actually playing the character that the DM is told they are playing rather than acting out some sort of other fantasy.