Dark Brotherhood. Not only because the repeatable quests are the most enjoyable, but you get paid handsomely and Shadowmere is awesome.
I like college of winterhold, mostly cause I like winterhold. It's cosy, I wish you could have a house there
Thieves guild, but only because my primary char is ALWAYS a "reappropriator of goods".
Sadly, the "fetch, get paid, do it again and then we'll advance the story" started getting stale after the first guild. When it started to repeat itself, I just rolled my eyes and chugged along.
Now, I avoid them all on a replay. They're just so damn tedious and the rewards: not so great when you consider they're already useless by the time you get them.
I even thought Shadowmere, a spectral horse, was the best present a guild could give me.
That is, until I saw it run up and try to take down a dragon.
Yeah, that didn't go too well. I ended up with a dead horse and some bones.
A spectral horse. Dead. Yep. Sums up pretty much every guild quest in the game.
The Thieves guild is the best one for many different reasons. First of all it has a grate story line with the Nightingale thing, the extra jobs gives an immersive gaming experience and you get some really good equipment out of it.
The Dark brotherhood is IMO the worst of them. Just too... I don't want to use the word evil but ghoulish maybe or morbid. The assassination jobs just feels tedious... never finished those quests so maybe the story line picks up later on but I feel like the story line for them feels rushed and badly written. If I had designed the concept of the Dark brotherhood I would have made them more business like, giving them a bit of a black ops CIA vibe.
I liked the Theives Guild the most, besides the nightingale crap.
I also liked the Thieves Guild the best, even though the story didn't make a lot of sense at times.
I like the Companions best. I like the story, the ideas behind them, and most of the members. Even their rivals are enjoyable, in a fun-to-slaughter kind of way.
The DBh is a close second, though not every character joins them, some kill them all instead. Everyone becomes a Companion.
I like the College of Winterhold well enough, but completing it kills off a character I like a lot. Granted, resurrection with the console afterwards is easily done, and as far as I can tell consequence free, but the very idea saddens me.
I don't care for the Thieves' Guild at all. Though it is quite funny to make up my quota of loot via the Black-Briar house, otherwise I'm just not a fan of stealing, and the strong-arm tactics do not appeal to me in the least. It all feels so petty. (The only one I like in the Guild is the one everyone else seems to hate too, which probably just means I'm weird.) I even found a mod that lets you wipe them out almost entirely, only leaving a few related to other quests.
it's a common sentiment, I've noticed. I even get why, I just don't feel it. She makes sense to me, and I like her voice.