Q:
Returning Player - Can't decide on class
A:
All of the classes and their respective elite specs are strong in their own fields, and picking one is entirely a matter of your personal preference, nobody can name the one most ‘entertaining’ class since they are all different and appeal to different people in a different way. Also, there’s no big differences in the leveling experience; some classes do more damage than others and some have better sustain than others, but that’s about it.
First, I suggest you study the classes a little bit; read about them in the Wiki, watch videos on Youtube, and read the profession sub-forums here. Try to decide which class seems the most interesting to you and also keep your preference on tank/support/dps in mind. This said, most of the professions can shine in multiple areas depending on the builds, so there’s no absolute pick for a single role.
So again, it all comes down to which profession seems the most appealing to you. I hope you find yours, and welcome back to Tyria!
One of the best ways I can try to help is simply suggest to try everything. If you have Heart of Thorns you get an elite spec you can utilize to change your class up a bit. One way to check out what different skills and weapons can do is to enter the PVP lobby and take on the training golems. It can let you get a feel for the class, its traits and skills, and how you want to handle it.