Angel is Buffy's true love and always has been. This was hinted throughout the seasons after Angel left at the end of season 3, ie. the crossover episode "I Will Remember You" in Angel (despite Buffy and Riley's ongoing relationship at that time), then again in seasons 6 and 7. That's why when Buffy said "I love you" to Spike, Spike said "No you don't, but thanks for saying it." Spike knows that deep inside, Buffy might've loved Spike for what he has done and for being there for her, but not in the same way that she loved Angel.
Airam
.... in your OPINION.