Depends if your playing PVP or PVE and what sort of content your doing instances/heroics, Naxx10/25, Ulduar?
For PVE my guild raid Ulduar 10/25 and the top 2 dps are nearly always enhancement shaman and retribution paladin. The 3rd spot is always different depending on luck, what fights were doing etc. It is usually between a mage, hunter, lock though for 3rd spot.
A good place to look for some really detailed info is www.elitestjerks.com they have amazing breakdowns and simcrafts of all the best specs and with the 3.1.2 patch out today quite a lot has changed, again.
If in doubt play what you enjoy to play and screw everyone else!