im not a lighter but what lampoly was saying is to desaturate your image and do lighting that way. youll get strong lights/darks. adding color is really the last step after that.
if you take your screenshot and desaturate it, you get a bunch of midtone greys. no real contrast, no real lighting. adding color isng lighting.
i did a really quick paintover of your original screenshot. top one is untouched.
you need to really push the darks and lights more. then worry about color.
but im not a lighter or anything, just my 2 cents.
oh also, your water is throwing the whole scene off. try fiddling with the material or copy it and make your own, but either way, the cubemap is totally wrong for that environment. you need a darker one, not a cloudy day cubemap.
anyway, best of luck, i hope this helped. im teh nub