Favorite, hands down is the EMH. Picardo's performance is just magnificent, especially with his wit and dry humor. McCoy is the runner up. He's opinionated and stubborn at times, but his concern and care is earnest. I'd trust him with my life, no questions asked.
Least favorite is Pulaski. While I found her more intellectually entertaining than Crusher, her personality came off as a bit sterile... just like Muldaur. I don't get why a notable number of people don't like Phlox. I found him quite refreshing on Enterprise