I have created a thief and ranger, and I have to say the ranger is way more fun to play. At least early game. I have heard many people complain that thief is not very fun early game, but I have not played it enough myself.
I have been totally loving the ranger class. I have a lvl 53 ranger and I have really enjoyed playing it. They are also thought to be one of the most over powered classes as well. I have not played an elementalist, but they look like fun as well.