Favourite Romance?

DAO, I'd say Morrigan, though I really liked Leliana, Alistair and Zevran as well (in that order).
DA2, Isabela, though I only tried, recently, Zevran. Merril hit the weird sister vibe with all characters I made, and Anders, although it'd be interesting, required for me to do a volontary tragic playthrough, which I need a particular modo to do.
DAI, I'd say Solas, though he's not my Canon romance (Cassandra).
ME, I rate them all more or less on the same level.
ME2, Miranda and LOTSB Liara.
ME3, I'd say Liara, though I like Miranda's content, despite the shortness of the dialogues available and some things I don't personally liked.

DAO: Morrigan
DA2: I don't know. Probably Isabela
DAI: Cassandra

DAO: Alistair - though I haven't completed my Zevran game yet, so that could change.
DA2: Fenris
DAI: Either Bull or Cullen. And Solas.

DA:O - Morrigan
DA2 - N/A
DA:I - Never Played.

DAO: Alistair
DA2: Fenris.
DAI: Solas.

Overall, my favourite romance would be Solas, with Fenris a close second.

DA:O Alistair ..... My 'canon' play through was a city elf rouge who made him King with Anora as his Queen then stayed on as his very public mistress.

DA2: Fenris ..... Once I heard the voice actor I couldn't pick anyone else, not my canon PT but my fav none the less. Canon is Isabella.

DA:I Cullen ..... I had a really hard time getting around to playing his LI as my mind was somehow firmly stuck on 'Cullen belongs to my mage Amell dammit', but I do love his nervous bumbling.

DAO: Alistair.
DA2: Anders. Haven't tried Fenris yet. Couldn't get past his hair. Might have to rethink that as Anders was a bit of a dud.
DA3: Solas. Cullen is my runner up.

ME: Kaidan. Entire trilogy. My first digital romance.

Just for shits and giggles I'll add my Bethesda romances as well:

Skyrim: Marcurio
FO4: McCready

DAO - Leliana, followed by Alistair
DA II - Isabela
DAI - Cullen, followed by Casandra

Leliana
Isabela
Solas

I've only started and completed Inquisition so I can't compare the other two. I heard that Solas' romance was the most popular so I started off with a Dalish Inquisitor to romance him.
Thing was, the more I progressed the more she seemed to be drawn to Blackwall. Did not expect that. Sure, she and Solas had a lot in common. They were quiet, thoughtful, academically inclined. But it never seemed to go anywhere beyond respected colleagues. With Blackwall, there was an unexpected sense of kindred spirit for her. He was a wanderer, despised wherever he went because of the past, never able to truly rest, never at home anywhere. To her, he became a symbol of everything she felt about her people: flawed, horrible decisions made, looking for ways to take back the past but never able to. If she could not forgive this man, a human whom her people taught her to be wary of, then how could she ever expect her people to be able to move forward if no one else will let them? What right does she have to hold a grudge against him since she's lived her life on the receiving end of human grudges?

So I tried again with another Dalish inquisitor. A proud one who fiercely believed in her clan, less philosophical and more suspicious of humans.
She punched Solas.

So here I am working on a third one, praying that my roleplaying won't go elsewhere again.
...right, favorite romance. Went off tangent. I guess my favorite is Blackwall right now because his romance got me to feel something about the interaction between the Inquisitor and him. Second is the Iron Bull since he fitted so well with the second Inquisitor's attitude.

Yes! He followed my character around Skyrim as she searched high and low for her twu wuv. She finally realized that he'd been there all along and they got hitched.  )

Favourite Romance: Zevran

Favourite Romanceable Character: Thane

Most Reliable Source of Torment: Solas