I've only done two romances to any length, the Trooper and Smuggler one.
I really liked Aric to begin with, he's a hard *** but a fair one, and that sort of resonated for me but then the romance started and it was the most awkward and forced thing ever. I just couldn't get into it, it ruined my enjoyment of the Trooper If I could get with Dorne I think I'd be much happier, but oh well...
But Corso, Corso was like a romantic dream. Nothing too flashy or special from first glance, I was a bit put off by his gentleman mindset and he obsession with guns at first, but then I actually felt like I got to know him. He seems so set on travelling and seeing the world beyond the farm, and then you realise that deep down he's the kind of man who really is just looking for the right place to settle down. He just melted my heart, and his adorable chivalry became something I loved, even his 'farmboy' title kind of became something I felt was endearing.
So, ATM I'm saying Corso is the best romance I've experienced, it's better than any other that I know of in any game.