I am a shameless Stephen King fan. I honestly think he writes better than any other modern, popular writer I have read. People have a tendency to get hung up on the genre, and the lameness of almost every movie that has been made out of his books. But he has written some of the best books I have ever read. Of his books, the ones that stand out are:
The entire Gunslinger series
The Eyes of the Dragon (Just finished, and really liked it)
I also like Michael Crichton. I do think he makes his books a little too "Hollywood-ish." But he researches his subject matter well, and his books are great reads, usually - the kind that keep the pages turning.
Patricia Cornwell is the same way. Page turners.
John Case is good, although he hasn't written as much.
I've liked everything I have ever read by Ken Follett.
I think I have read every book those five has written.
On the other side of the spectrum, I just finished reading Digital Fortress, by Dan Brown (author of the Davinci Code). It was okay, until the last hundred pages. Then it became almost embarrassingly ridiculous.