I did a quick edit on the man, both with and without a black outline. I tried to clean up the shading a bit, and put some more detail into the face.
The scene could certainly use some shadows to give it a bit more depth.
And like every other isometric pixel art piece thats ever been attempted, its all about the little details that give it life. cars, more people, animals, smoke, etc all add up to make these sorts of scenes more than the sum of their parts. Just keep adding things (as long as they're consistent with the style of the other bits) and you can't really go wrong!