How can I achieve these(attached)effects?

I'm working on a game design and my teacher doesn't seem to be happy with the graphics(proto x). He wants me to give the graphics a look like the attached "jet pack joyride". But I'm having difficulty achieving that effects. As you can see the difference that my graphics look more flat while joyride's graphics look more 3D and nice.

Can someone here help me by directing me to a tutorial or giving some instructions here that how to achieve that in Illustrator or photoshop?

I would really appreciate that. Thanks!

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