Alistair added a lot of personalilty to my games. I tend to prefer him as the main romance because:
1) We both have a common goal -- the Blight. We're carrying the same banner out of respect towards Duncan and the soldiers that have gone before us. (This reason doesn't apply on characters that were foricbly conscripted though.)
2) I enjoy Alistair's sense of humor. For some reason, I don't like him as much on my male character because even though the dialogue is the same, it seems inappropriate and irritating at times. I can't really put my finger on it. I definitely do get why some male players just don't like him. (To be fair, Morrigan is just as snarky and annoying during the female PC romances, too.)
3) He has a good heart. He really does. I can handle most of the dumb choices and bad results when good intentions were meant.
4) He says what's on his mind. I understand the comments about babying him, but he did most of the emotional work in the some of the romances from my perspective. I didn't feel like being the pursuer nor did I go out of my way to flatter him. It worked out that Alistair was the one that took the risks by wearing his heart on his sleeve to see if my character would be be interested in return. And then once the approval progressed into love, he flat out declared his love and basically says, "See? That wasn't so hard. I love you!" I found this very realistic because personally I can be bad about expressing my feelings and my husband will be the one to pull me out of my shell since he is not shy at all. I appreciated Alistair spelling out his feelings clearly as opposed to Zevran who will never actually say the same thing. Zev has a lot of good qualities, but this is one of the striking differences between the two men in self expressions.
5) Lots of room for character growth. He did grow as a character during the game. Probably not as much as some would have liked, but the some of the epilogues seemed to indicate that he rose to the occasion. I have hopes that we'll be seeing a more mature Alistair in the expansion, but he could just as easily be the same guy we know. (Case in point: Duncan was not always the noble man you saw in the origins either.)
And funny enough, I knew about the writer being inspired by Xander (one of my favorite characters because of his sarcastic lines) from Buffy, the Vampire Slayer and I definitely saw similiaries. I remembered being upset with Xander for letting the love of his life slip through his fingers and not fighting harder for her. I was surprised to find myself getting just as upset with Alistair for similiar reasons and for not seeing it coming in advance. (Boy, do I have an axe to grind in the expansion if my character ends up running into him again.) They're both dumba***s!