I never really hit it off with Alistair, even before turfing the guy for Loghain. I molly-coddled the whiny, Carth Onasi-esque brat, but he just could not get over me using blood magic to sacrifice his precious Isalt. Sheesh, kid, it's not like I was going to run off to the Tower of Mages, I'm on a schedule here.
Combined with that and how cool Teyrn Loghain was as a character (if you get him, have some conversations with the guy - interesting fellow, that) it was a painfully easy choice to ditch him. I never got along well with Morrigan either because although my Dwarf Noble tended to be painfully self-serving, she also did Right Thing if given a chance, and Morrigan wasn't keen on that. Despite this I did maintain a reasonable if slightly frosty rapport with Officer Sun and she stuck around throughout the game.
I was more succesful with... well, everybody else, actually. They all mostly warmed to me (though Oghren not so much) and I got to do most I think of their quests. This is because I habitually court the approval of my characters as much as possible whenever I play an RPG, I tend to bring them aside for multiple chats and say whatever it is I think they want to hear. In my defence story-wise, my characters tend to be duplicituous, politically-minded bastards, so it makes sense. Took me a while to recognise the all encompassing power of Gifts, but once I did I sort of aggressively went after those too. I think gifts and potions were about the only things that stayed in my bags.
Sten was a goddamn monster on the field as a tank and a preferred character for a long time, though I occasionally alternated him with Shale - Alistair I found comparatively useless, because I was lazy and set all the characters to autolevel and guess who never got taunt? That feckless brat...
And I wound up falling in with Zevran in the end, more or less by accident - I was courting the appeal of just about everybody but he seemed to be the only one I activated the romance story for. That romance didn't really seem to go anywhere for my Aeducan cutpurse, but ne'er mind. She's now back in Orzammar lording it over her house and awaiting the sequel where she probably will not be mentioned.