Love the responses in this thread 
For me, it's so hard to pick any one ensemble, but it would have to go as: DAI > DAO > DA2.
DAO: The originals. Morrigan, conflicted as my canon Warden ended up feeling for her, is such a great character. Leliana, Alistair, Sten, too. With the exception of Alistair throwing a tantrum if you don't immediately rush to execute Loghain, I love pretty much everything about Alistair. Sten's story, like Blackwall's, is fascinating for the philosophical questions it brings about. And of course, Zevran is endlessly entertaining, and his backstory is wonderful.
I think one of the things that makes DAO stand out from the others (particularly DA2) is that each character's backstory is so well-developed and nuanced.
The only DAO character with whom I never had strong feelings was Oghren and perhaps Shale-- but I picked up both of them late in the game, and never really had much time to get to know them, really.
DA2: Not as strong perhaps-- particularly on the backstory for each character (we barely learn about what their lives were like previously, and how they got here)-- but still a great cast. I love the character Anders, though him as a person-- not my fave. Similarly, Fenris is a grouchy mage-hater, but he's hilarious and I loved his backstory (one of the few). And, of course, Isabela. Isabela's quote "Our mistakes make us who we are," might be one of my favorite character lines in all of the DA universe. It's particularly poignant that she says it in banter with Anders-- who is more identified by his rights/wrongs than Anders?
I liked all the other characters, of course, but never connected with them the way I did with those above, or at all like those I did in DAO and DAI.
DAI: The first one I played. Dorian is probably one of my favorite VG characters ever, Cassandra is my favorite LI in the DA series, and Varric is even stronger in DAI, imo. Oh, and, um this minor character named SOLAS aka BEST EVER.
Also, his location-specific comments, and his general philosophy on life is pretty much everything I agree with. I disagreed with him on one or two quests, but other than that, Solas is like bromance 500 for my Inquisitor.
Cole is fascinating-- someone above commented on how they use him as a narrative device to develop backstories, right on, that's brilliant.
Blackwall's banters are wonderful ("there can only be one" with Sera is amazing), and his character raises such interesting philosophical debates. I still go back and forth on them in my head.
The only character I can never warm up to (can anyone? I'm genuinely asking, I would love a reason to like her/sympathize with her) is Vivienne, and I tried so hard to like her. I put her in my party in my most recent PT and her first banter, she insulted Varric for no reason whatsoever, in her typical fashion. GET OUT VIV. YOU'RE GONE NOW. Also,
But seriously, I can't find anything likable out her, and I'm trying.
The banters in DAI are so strong, too. Solas and Iron Bull discussing politics and philosophy (and playing chess!), Cole eventually growing on Cassandra, Dorian & Sera realizing they love each other, etc. It's all so lovely and wonderful, and I love how the relationships grow throughout the story.
tl;dr: I love all of DA
, cheers