Thanks so much for all the feedback! I really appreciate it. Here is an edit with what I've learned.
How else can the color be improved?
How about the UI?
Also, is the 'camera' a little low or just right?
The idea for this mockup is an action platformer type with puzzles and combat. How can I best communicate that?
I agree with Willsaber.
The problem with the 2nd one is that the background is incredibly dark. If you are trying to put more emphasis on your monsters and stuff- then I'd say either make your background lighter and your foreground objects darker- or do the opposite: where you make BG darker and make the FG lighter.
Ia also think the main character (the guy with the hat)'s colors are very off from the style everything else in. He's a bit too saturated compared to everything around
Other than that, I think it looks awesome! :D