Hmm. The yellow sprites do stand out pretty well against the (rather dark and unsaturated) terrain tiles. I do wonder how easy it is to quickly tell one sprite from another, though—they all have the same limited, low-contrast palette, and it's often distributed rather similarly. The life/energy/whatever-they-are bars hovering over the individual sprites' heads are difficult to pick out where they happen to overlap with another sprite, so I hope it isn't necessary to the game to be able to figure out the readings on them quickly.
The dark sprites (enemies, I presume) aren't going to stand out nearly as well as the yellow ones. That's a potential problem from a gameplay perspective.
The animation looks smooth, and I think it's telegraphing the movements clearly. Realism isn't that much of a concern when the sprites are already this stylized. (Take that with a grain of salt, though—like cels, I'm not exactly a master animator.)
From a purely artistic perspective, cels is right: you could do with more contrast. On just about everything.
From a *game art* perspective, making the enemies stand out more (and making it clear which sprites are enemies) is probably the most important thing. My suggestion would be to never use yellow on the enemies, only the blues and grays (and make sure each enemy has at least some blue on it, so that it doesn't vanish into the shadows). Pick a third accent colour for neutral units or objects, if there are any.
(I also wouldn't cover such a large chunk of the top-right corner with the UI, or at least experiment with it being in a clearly delineated area at the top or bottom, but I do realize that may not have been your idea.)