Wow, these look great! The only one I'm kinda worried about is Syclant. In the new sprite, his lowermost pair of icicle wing things are far shorter and narrower than the original. In addition, I think the angle of the wings should be changed. In the new sprite, they're almost perpendicular to his spine (yeah, I know bugs don't have vertebrae, but you get the idea). That wasn't the way it was in the original. Finally, I'd like to see more of Syclant's face in the backsprite (especially those awesome icy mandibles) but of course that's just a personal preference. Other than that, I love the posing and the overall design. I can imagine that Syclant would be a very difficult sprite to remake (what with his odd body shape and loads of little details) and this spriter certainly pulled it off with aplomb.
Edit: I love your prevo, Darkhuaza!
Edit 2: I'd actually like to retract the point I made earlier about the angle of Syclant's wings. The spriter who did the remake was simply trying to stay faithful to the original front sprite, and overall I like their design better. No offense to Syclant's original spriter, but it doesn't make sense to have Syclant's wings spread out all around him in his frontsprite, then fold them back in the backsprite so you can see his face more clearly.