I liked Alistair for most of the game. The fact that the death of Duncan got him down seemed very natural. The only thing about him I did find annoying was at the end of the game. On my first playthrough I decided to make him marry Anora and become king, and convinced him to go along with it. And even though he had agreed that it was for the best and that he'd go along with the plan, he still came complaining about it to me on three different occasions. Dude, you said you'd play along, so play the fuck along already. Don't go blaming me for a something you agreed to do.