For the current writers on this forum, I've really enjoyed jennifer and BigB's stories along with Fesselfan's stories. But everyone's stories have been great as well. They've really sparked some life into the forum.
However, if you want to talk "old school," you have to include Gillian B. and PH up there with Mason and Doug R. I also used to enjoy Lisa's stories from the 2002 archives. I found her style of writing so well that I've adopted some of it into my own stories as well.
From this current board I would have to go with Jennifer hands down - from the old style (I've been reading these for a while) I would have to go with mason and SilentSimon - both great writers and great stories, the attention to detail and writing style are what really make all of their stories the best