Imperial Agent - Hands down the best out of all the storylines. It's James Bond in space. The voice actors who got this job need to be commended, as there's plenty of times when the Imperial accent isn't warranted, and they slip in and out of it perfectly. I think the 2nd chapter is the strongest because of the twist that comes early into the narrative, that basically you're so badass that you had to get reconditioned with an "obey me" codeword ala "Would you kindly" from Bioshock (but not nearly as subtle). That said, each of the chapters is very strong and I think the twist at the end of Chapter 1 might be the best in the entire game. If you play SWTOR and only want to experience the best so you don't feel like you're wasting your time, this is the story to play. 10/10
Smuggler - I think this is one of the more fun storylines to play through. The smuggler character has such a smug sense of satisfaction at EVERYTHING they do that's it's nearly impossible not to like the character, even when they're being complete and total assholes. Best part of the story is near the end of the Alderaan set when you have to go and act as a noble's champion in a duel. As soon as the other guy says he's ready you shoot him. He screams at you that he wasn't ready yet, collects himself, then asks to go again, so you shoot him again. Just hilarious. Some of the twists and turns of the overall story kept me guessing as to what was next and there was a particularly satisfying twist on the latter half of Chapter 3 that I had a good smile at. This one is definitely worth your time if you're not into playing for the bad guys. 8/10
Sith Warrior - 2nd best Empire storyline and made so largely because of Darth Baras. While the first chapter isn't much to write home about, there's a fairly satisfying conclusion to it, especially from the Light Side standpoint. From there you actually go into furthering the overall galactic conflict but the twist at the start of Chapter 3 is just awesome and while the effort through that final chapter is largely self-serving, that you're doing it as the right hand of the Emperor is pretty awesome overall. 8/10
Jedi Knight - Probably the one storyline in the entire game that makes you feel like an actual hero. Chapter 1 is just you saving the day over and over again. Chapter 2 itself is kind of a step back but it leaps forward at the end and things take a darker turn. The twist at the start of Chapter 3 is sweeter if you've read the novel Revan. It's also hard to top the conclusion to this storyline as a whole. 8/10
Bounty Hunter - I enjoyed this story a lot even though until Chapter 3 it's very self serving. However it really fits the character of a Bounty Hunter to a "T" and each planet just has you going after high profile bounties, though each one is fairly interesting. Some of the story twists aren't anything to write home about though. Chapter 3 has you serving the interests of the Empire, which is a nice change of pace, though in the end it's also a self serving move. 7/10
Trooper - I think anyone would get a kick out of this story if you played Dark Side choices and asshole comments. However, it's pretty sedate on the whole and just doesn't grab you like some of the other stories. Chapter 1 is interesting as you work to hunt down the traitors of the original Havoc Squad but it goes south from there. Chapter 2 is just one big recruitment mission and Chapter 3, while playing into the galactic conflict overall, is just an extended recruitment drive. However, I think it has one of the best individual moments out of any story next to the one I detailed up above in the Smuggler. In between Voss and Corellia your side mission is to attend a senate hearing on your actions as Havoc Squad. The kicker is that it's being run by a senator working for the Imperials. You're told to play it straight, given evidence that the guy is a traitor, and are supposed to present it at the right time. The first conversation choice, however, has the option to just shoot the guy. So I did. The reaction from the NPCs was priceless. Eventually one of the senators says, "Just go back to the war where you belong." I couldn't stop laughing though, just too funny. Anyhoo, single bright spot doesn't take away the dullness of this story. 4/10
Sith Inquisitor - While I play an Assassin as my main, I have no problem stating that this is the worst storyline in the game, by far. You play Indiana Jones in the first chapter, the twist at the end is very easy to predict (well, half of it at least), and the story writing at the start of chapter 2 quite obviously didn't get an editing pass. You're attacked, you survive and are rescued by your apprentices in your office. Later, on your ship, it's as if that never happened because you ask what happened and they say they pulled you out of a ditch. The entire story is self serving, has no impact on the galactic conflict at large, and your single best moment at the conclusion of Chapter 3 is stolen from you by an NPC. Stay away from this storyline unless it's the last one left. 1/10
Jedi Consular - Second Worst story, only saved by the fact that you start serving galactic interests in Chapter 2. Even then there's no twists that can't be seen from a mile away, and nothing really all that interesting about the story as a whole. 2/10
