All of those shots are underexposed and the lighting really isn't flattering. Sorry for being so blunt. Don't do direct flash, bounce it or diffuse it. Go back like 10 pages on this thread, a lot of people have some tips and advice.
For the most part, I agree. Not ALL are underexposed, but a great many most certainly are. Just check the histograms. If the poster allowed editing, I'd be able to illustrate just how much better the images would look if exposed properly. Great shots, but poor exposure control. Of course that is only my opinion as well.