it's an old thread but i'm new so i'm going to add my two cents:
I really liked the idea of Cordelia and Angel, and was really hoping they would get together. (I think if she could somehow come back from the dead then they might have a chance.) That said i think that angel thinks his true love is Buffy even though it is obvious that he uses her as a crutch, a safe alternative to actually having a relationship until he starts seeing Nina.
Angel mourned Buffy's death, dealt with it and moved on. When she returned from the dead he saw her offscreen but returned to the hotel with a renewed incentive to do his work. He showed no evidence of pineing for Buffy, on the contrary, He was way less broody and his feelings for cordy begin to intensify. His appearance in sunnydale at the end of Buffy season 7 does nothing to convince me he 'in love' with buffy. All he wants to do is talk about Spike! in season 5 its only when cordy is in the coma and spike returns that Angel remembers that 'oh yeah, that's right, i'm in love with Buffy'. It is more about his competativeness with Spike than his great love for Buffy.