Lighting is a good tip! But don't think about it as an actual set with actual lights. Think about it as a painting. As a rule, we usually do our lighting through a combination of a single directional light, ambient color and fog. Experiment with the colors of these until you get a nice result (aim for painterly realism -shadows can be purple!- not photographic realism).
When in Unity, also, an easy trick is to simply add a few post-processing filters. Glow makes everything look good!
And finally, another ToT trick: fill the air! Floating particles really make your scene feel alive.
Remember that
it is not the engine that makes the difference, it's the art direction!