If Angel had never appeared in Buffy's finale or the events of TGIQ happened, i'd totally be going for Cordelia.
Their relationship was far more adult. It was based on Friendship, Love, loyalty, honesty and trust which does mean a lasting relationship.
There was a definite attraction in the very beginning for Cordy, and it would be an absolute lie if Angel said he'd not thought Cordy was attractive so the argument
'And doesn't anyone remember when Cordy tried to flirt with Angel on Buffy? He wouldn't give her the time of day'
doesn't hold water. He was in love with Buffy. Doesn't mean he didn't appreciate Cordy aesthetically.
Also this comment was totally wrong
The REAL Cordy NEVER would've fallen in love with Angel.
I'm sorry, but WTFunk. REAL Cordy?
Which Cordy wasn't real?
The One from Buffy? Watch Out of Sight, Out of Mind. This, for me, is the closest we come to see the 'Real' Cordelia on Buffy. That vain, vacuous bint that you seem to be implying as the 'real' Cordy is nothing more than a self defence mechanism.
When Cordelia grows up to the woman she was destined to be, she truly becomes someone who could love Angel.
The thing I hate about this relationship is what the writers did.
First off, hours after the events of Home, we are led to believe Angel is with Buffy with that whole Cookie Dough speech.
Then weeks after Cordelia dies, not only is Angel getting it on with a Werewolf he is also travelling across the globe over some petty jealous thing after Buffy again.
Because of these, i'd have to say his feelings for her weren't genuine, but honestly, i think they were, its just the writers didn't know how to work Buffy and Angel into the smae episodes without it being about their relationship. It totally pisses all over the sacrifice and memory of Cordy.
So, i'd have to say Buffy and Angel in the context of your question.