THEY ARE ENGAGED/MARRIED ALREADY. In AC, they show her ring and how she wants her to move on off of Aeris's death, because now they have their own lives ahead.

And Cloud doesn't love Aeris. He always thinks of her, because he is heart-broken that he let her die and witnessed her death 2 feet away from her and didn't even try stopping Sephiroth.

Plus, Cloud n' Tifa make a better couple anyways. And Aeris found interest in Cloud because he reminded her of Zack. She reminisced of Zack, but didn't love Cloud. If anyone, she loved Zack. I'm not hating on Cloud and Aeris fans, but I think Tifa and Cloud match much better.

The only reason Aeris and Cloud could be cool is because Cloud's mother told him that he should find a girl slightly older than him to take care of him.

BUT the biggest reason Cloud probably loves Tifa is because....well her chest (I had to mention her bust somewhere in this post.)