SWTOR:
I'm finding the Sith Inquisitor story arc to be surprisingly good, with a few moments of weakness that hold it back from being truly great. The Sith Inquisitor is one of the funnier characters, behind the Smuggler, particularly in his more "differently rational" moments. And with the exception of the entirely superfluous Xalek, he has one of the best groups of companions in the game.
Khem Val is an 8 foot force-user eating monster who has been trapped for eons after serving one of the greatest Sith Lords in history, and he makes it very clear that he initially finds serving you to be an appalling demotion. Despite that, he has a unique charm to him and his slightly antagonistic relationship with the Inquisitor is surprisingly well done. It also makes it more emotionally resonant when your character manages to impress him, and when events take a turn in the plotline it actually matters. Also, mechanically, he's a melee tank with powerful hits and AoE damage, which is a great pairing for a squishy wizard or sneaky rogue (basically the two specializations for Inquisitor).
Andronikos Revel is a space pirate (previously a space cowboy) who's personal quest for vengeance runs into your quest for an artifact, and despite being billed a violent loner, rather easily (and wisely) decides that teaming up is a much better way of going about it, and once that's done, he decided to stick around because, well, you've got a ship and freedom to more or less go where and do whatever you want. He kind of takes a lot of the Sith weirdness in stride and is generally a useful companion with a good array of spacer lore that helps with your mission. Mechanically, he's ranged DPS / tank and is quite an asset for a melee-centric Sith Assassin.
Ashara Zavros is a Togruta Padawan chafing under the tutelage of some particularly stupid Jedi Masters. Proud, passionate, and an exceptional fighter, she is frequently admonished for her aggressive nature and willingness to do what is necessary to achieve the objectives. At one point, her Master needs a team to repel a Sith / Imperial assault. He names several students, not including her. She says, "Master, I should go with you, I'm the most skilled with a lightsaber of all your students. (one of the students named) barely knows which end the blade comes out of." The Master says, "You need to learn restraint, obedience, and to show compassion for people not as skilled as you are. Stay here and watch the supplies or meditate or whatever." Needless to say, when the Sith Inquisitor shows her some forbidden knowledge from a Holocron (her own Masters wouldn't give her access to a Holocron) and appreciates her for her Sith-like qualities, she goes over pretty quick. Especially when its clear that her Masters are incompetent. That being said, she maintains that she is Jedi (unlike Jaesa) and never goes Dark - she attempts to convince the Inquisitor to ally with "Grey" Jedi in order to bring peace to the Galaxy as a whole. Essentially, she realizes that if the Jedi drive back the Sith, they'll go underground, scatter, and build up in secret to enact their revenge later (which is precisely what they'd done leading to the prior conflict); if the Sith conquer the Jedi, they'll immediately start fighting among themselves and collapse their Empire from infighting; only a group that is both and neither can bring a lasting peace. Mechanically, she's a melee character with dual lightsabers and the love interest for the male Sith Inquisitor. The relationship is actually pretty well done, and her friendships and lack thereof with other characters is mentioned as well - Andronikos shows her how to pilot the ship and tells her spacer stories, etc; Zash mentions that Ashara clearly doesn't trust her when they work together (and that's a compliment; Zash should NOT be trusted), etc.
Talos Drellik is an extremely gifted, if eccentric, Imperial Reclamation Services officer. An expert at deciphering clues and getting into ancient tombs, temples, etc, he's naturally quite useful to the Inquisitor and given that the first half of the Inquisitor's storyline is basically "go to this ancient place, get the artifact, etc", he's extremely keen on hearing about the Inquisitor's exploits and sharing in them. Optimistic, energetic, clever, and quirky, he finds the entire "absorbing Sith Ghosts" part of the story to be incredible. His view is that the Empire can learn a lot from studying its past - the leaders, the events, the bloodlines, all of them form a foundation for the current Empire to build on. He finds Khem Val fascinating but admits that Val doesn't like him much - Khem Val only respects strength and Talos isn't a mighty warrior (though he's no slouch, he's just not a powerhouse).
Xalek is a very good character concept that is added to the game so late that he barely matters to the story. He's a Kaleesh, which is the same species that General Grievous started out as. He's more or less a 'trophy apprentice' that the Inquisitor acquires to show off with; an apprentice from Korriban Academy is considered to be a mark of distinction for a Darth (this is mentioned both in the Sith Inquisitor storyline and in the Sith Warrior storyline). He is an expert killer using a double-bladed lightsaber and seeks to attain Sith Lord status because that would make him like a demigod in his people's culture. He barely interacts with anyone else in your crew and is blunt and to the point.