sometimes lwf gives a flat result.Neil blevins discusses this in article http://www.neilblevins.com/cg_education/linear_non_linear_visual_difference/linear_non_linear_visual_difference.htm.
how do you deal with this?
Turn on Blender’s Colour Management.
This is out of date, but will explain the basics:-
http://archive.blender.org/development/release-logs/blender-256-beta/color-management/index.html
You can also make Blender aware of your monitor profile if you use one. More information on how to do this is here:-
EDIT - Here is an explanation tailored more specifically to the question asked
If you want more contrast, add it in post. I think that the problem is not “flat light” but the situation where people have gotten used to the look provided by render engines that operate in a way that is not physically plausible. It is clear that when you use gamma corrected textures without linearizing them and incorrect light falloffs you get more contrast because light does not “add up” as it should anymore. When you double the light that produces that “50% gray” surface, you should NOT get a “100% gray/white” surface but a “flat looking” surface with about 63% “gray”. If you do get 100%, it is not correct despite the fact that the result might look pleasing.