Most classes are nice to play if have the right build and you like the play style.
Two things that could be useful to think about before you pick a class:
1) Race: not all classes are available to all races, so if you care about your character's look, then that may limit your class selection, still, there are many choices for each class. The race selection also impact on which faction you pick: League or Empire.
2) The other thing you must take in account is the rol you want to play in a party. This is defined by the aspects. All classes can be dps (important for lvling) but not all can be tank, healer, support and crowd control.
Here you have a talent calculator:
https://alloder.pro/calc
Warrior: dps (Aspect of Assault) and tank (Aspect of Defense)
Paladin: dps (Aspect of Assault) and tank (Aspect of Defense)
Scout: dps (Aspect of Assault) and tank (Aspect of Defense)
Healer: dps (Aspect of Assault), healer (Aspect of Healing) and support (Aspect of Support)
Summoner: dps (Aspect of Assault), healer (Aspect of Healing) and support (Aspect of Support)
Warden: dps (Aspect of Assault), healer (Aspect of Healing) and support (Aspect of Support)
Mage: dps (Aspect of Assault), support (Aspect of Support) and crowd control (Aspect of Suppression)
Psionicist: dps (Aspect of Assault), support (Aspect of Support) and crowd control (Aspect of Suppression)
Bard: dps (Aspect of Assault), support (Aspect of Support)
Engineer: dps (Aspect of Assault), support (Aspect of Support)
Plz correct me if i made a mistake with the aspects
P.S: at top level there is a quest that let you unlock a 2nd spec. So you can have 2 builds (this is useful to have a pvp and pve build and/or play different aspects)
(edited) thx