I think each DPS class is going to be best depending on the situation. All I can do is echo the previous posters, and say play whatever you'll enjoy the most. Enjoy burst melee DPS? Dragoon. Sustained melee DPS? Monk. Burst/Sustained ranged DPS? Bard. Sustained ranged DPS? Summoner. AoE/Ranged DPS? Black Mage.