My $0.02US:
Prologue: Sith Inquisitor
Chapters 1-3: Jedi Consular
Going from the other direction:
Jedi Consular - already played it through level 50 and playing it again (currently just finished Chapter 1 a second time). This is simply the story arc that makes me feel most like I am participating in the Star Wars universe rather than having an individual adventure with a Star Wars backdrop. That, plus the realization that a timely, subtle Force Persuade can often be as effective (or more so) than a lightsaber battle makes this my favorite line.
Jedi Knight - played this one up through Tattooine and just felt petered out -- there are a lot of 'you have to stop the Empire from completing their super-weapon' story arcs, both planetary and chapter-long, and I think this one just triggered my sense of fatigue over the trope. That, plus it seems that the Knight gets companions at a slower rate than any other class in the game, so you have less opportunity to 'change things up' by swapping out your sidekick to get a fresh perspective on things.
Smuggler - loved, loved, LOVED, Chapter 1 on the Smuggler -- second favorite after the JC -- Chapter 2 is interesting mainly for its connection to one of your companions (so if you're not really 'into' that companion, you're likely going to feel the story momentum from Chapter 1 slow down a bit), and while I slogged through the opening planet of Chapter 3, I just lost interest about halfway through the chapter. I may start over with a new Smuggler just to see if playing through the arcs with a different motivation makes them more interesting (my initial attitude was as a Han Solo, galactic grifter and scoundrel attitude, but the last chapter in particular seems much more focused toward Smugglers who are really true-believers in the Republic rather than out for their own gain).
Trooper - first time playing through this arc, and the twist leading up to Chapter 1 was more interesting than Chapter 1 itself, at least for me. Ended up putting this one on the back burner for a while but have recently gotten re-interested in it now that I've reached Chapter 2. Only problem? Chapter 3 looks like yet another 'stop the Imperial super-weapon' arc coming up. The good news is that the Trooper arc feels most closely connected to most planets' planetary arc (especially, surprisingly, on Alderaan, where I felt the Trooper and JC were playing two different aspects of that conflict).
Sith Inquisitor - my favorite of all the Prologues (though none of the prologues are actually bad, IMO -- they're all enjoyable); I had the happy accident of deciding to roll a SI who was certifiably insane with occasional moments of lucidity, which made the initial story much more entertaining. Chapter 2 has been OK, but hit the wall on Hoth and haven't been able to push past it to keep going.
Sith Warrior - the only class I haven't gotten out of Chapter 1 on - don't think it's a bad story, but it just doesn't push my buttons.
Bounty Hunter - yet another class I found awesome coming out of the gate. The Chapter 2 epilogue was something of a gut-punch, and it took the motivation out of running Chapter 3 for me, so my BH is still sitting on Belsavis in the starter base.
Imperial Agent - the story is great at giving you a lot of information and making you try to put it together in some way that makes sense, but the same story complexity makes it easy to say, 'ah, tonight I just want to kick butts/be a hero/something simple' and end up leaving the IA on the bench. There's probably as many cool moments in the prologue and Chapter 1 of the IA story line as any other class line, but they're so disconnected and challenging to parse that it doesn't add up to as cool of a story, IMO.
General observation -- in class storylines that present a well-developed 'villain' for you to contest against in a chapter, defeating that villain at the end of the chapter lets loose a lot of story momentum and makes it hard to get rolling into the next chapter.