For children's work this is an easy question, Cheryl & Nicole must be the winners. No one has the depth of feeling that they do.
For nudes I would have to say it is Thomas and Faye at the top.
Abstracts, of late Donald Miller's work has shown a very large leap in vision, substance and technique, not that it wasn't already pretty good. It just gets better.
Architecture, landscape and generally top of form would have to be be Francesco, but he hasn't posted an image in over a year. Jorge comes to mind as well.
Landscapes become more difficult, Steve Sheppard, Alex Hawley, Ryan, there are too many good ones here to list.
Technique and technical proficiency would go to Sandy King, as well as being an all around class act and mentor.
Heck, take a look at some of these folks and you will get a lesson in photography. tim
The work in the galleries is very rich and varied.
I'm not going to suggest my own personal favourites because, dare I say it, subjectivity plays a role here. It's not too unlike asking people what their favourite colour is....
I think the best thing is take some time to explore and make your own decisions.