I do like all of them a lot, allthough they are a bit cliche.
I pretty much have no knowledge when it comes to portraits, so I can't really describe what I actually think, but I would try making the flash less "obvious". They do look a lot like flash lit images, especially the second one, almost seems like a Copy & Paste-job. Also, I would pull back the exposure in number three a tad, it's a little bit too bright.