Well, I have to say that it is TIFA, cuz she is his childhood friend, and in the beginning, he said he wanted to impress her. He even got the guts to follow her when she was in the mountains that not even her friend could have done.

And another one is when Tifa went to the well and they made their promise to each other! And what about when Tifa take care of CLoud when he was in his vegetable like form? And about that highwind scene! And Tifa was the one who helped Cloud find himself.

And so I have to say that Cloud likes Tifa more, since they already has a history and he just met Aeris.

So, one point for TIFA!!