Really guys, such a vague description? Here i go: (not in order of best, as there is no best, but rather numbers are just for numbering)
1.Warlock- Assist class. Not great armor nor great recovery but built around smashing ads. Great abilities (i.e super, grenade, melee, skill tree etc.). BTW even one of the most overpowered primaries, the Tlaloc, is warlock exclusive. You can get it by reaching rank 3 with the gunsmith.
2. Hunter- Mostly the guy who likes playing tactically. The most effective way of playing as a hunter is by using long range weapons- scout rifles, snipers etc. Built around playing in the shadows and getting kills or aiming for the big guy. The hunter exclusive exotic is a hand cannon called ace of spades and its meh.
3. Titan- Basically the front-line dude. Great armor. Built around smashing everything in sight. Play on the front line. The most effective weapons for titans are auto rifles, side arms/shotguns. The titan exclusive exotic is called fabian strategy and it is the worst exotic.
Dont let me influence your judgement. I told you how each class was made to play but you can change that by changing your armor/recovery/agility stats and do something like i do- get a front-line warlock by stacking on armor and recovery. The rest of it is up to you. You can decide what type of skills you like in your character and then you can modify it using various builds. I personally chose the warlock because it has (arguably) the best skill tree and the stormcaller no super build (with claws of ahamkara instead of alchemists rainment) is an amazing build. Basically choose what kind of exotic armor you want and what kind of skills you want, just do a little research for yourself and everything will be a ok.
Hope i helped. Sorry if you thought that my answer was a little too long but the question was so that the answer HAD to be long :)