That Master Chief/Cortana one is a redo of one you did years ago, right? I remember seeing a similar image on ACF, and I've never even played whatever game they're from, but I do remember their names from your explanation of that drawing. And from what I remember of it, this is much more natural and less stiff. You should post the old one with the new one for comparison FGJ.
I agree that the FF4 one definitely needs some color, even if you only give it a basic coloring job. With all the lines, it's an incredibly busy image and just a tad monotonous. Color would help guide our eyes in picking apart the different objects in the image and the distance that separates them. Then I bet it would be epic.