Gotta go with Zevran. Morrigan is a little too much of a..well.. b*tch, for my tastes. Although I HAVE romanced her. Leli is very hard for me to romance as a male character....or a female character for that matter. Wine, Women and Song and the one for romancing all the different characters are two of the few achievements I STILL don't have. I like Leli...just more as a sister figure no matter what gender/orientation I play as.
My primary romance with Morrigan. But when she broke up with me later in the game I had a foursome with Lelianna, Isabella, and Zebra at The Pearl. We made up before the end of the game though. And then I followed her through the mirror at the end of Awakenings.