For DAO both Alistair and Zevran. But I like matching Elves with Elves so in that circumstance it will be Zevran. In the end though, Alistair might take the lead by half a point. Plus he can make me his queen. 
Anders for DAII. I mean, I like Fenris...but I dislike him looking so frail next to my Hawke. Plus, I always feel a little nostalgic when it comes to Anders. I loved him in Awakenings and was sad to see the 180 they did with him but...oh well.
And for DA:I both Cullen and Solas. And as Solas is race-gated (Which wouldn't have mattered to me anyway since I always would've romanced him as an Elf.), my Human girls get all snuggly with Cullen. I kind of like Iron Bull but he often makes me feel a little dirty so he won't be making the list.
Hard to pick one though....Could be Alistair since he was my first in-game romance ever. Or maybe Solas since he was the last and unlike Alistair, Zevran and Cullen, he offers no happy ending. As of yet, at least. Or Cullen as his romance is even sweeter and fluffier than Alistair's, and sometimes I just want fluffy. Or Zevran, who's heart you really have to conquer because he doesn't love easily.....So difficult and subject to change... But as of now it has to be:
1. Solas
2. Alistair/Cullen
3. Zevran