Play what you like is the good concensus, but some things to take note of.
If you like playing toons, or spend a good portion of your time goofing off rather than focus on one and grind it, I'd suggest starting out as a class that you can help buff/heal your toons through two boxing during slow times and/or downtime between fights. Shaman/Druid and to some extent Beastlords, is the optimal choice for players who prefer this method.
All can solo well, and each has their own perks to add to a group.
Shamans get Slow, Malo, a decent pet, best Stat buffs, decent heals, good dots and dd's
Druids get snare, damage shield, some HP buffs, good heals, decent dots and great dd's
Beastlords get the best pet, low shaman buffs, low heals, low slow, great melee
once you get one of these to high end, you can use them to speed things up your other characters.