What about Yuna? She is actually like Cloud searching for a dear person to see her/him again. I mean, Square has killed him and they are a couple, though. Same with Maria and Edward from FFIV. It can be seen really romantically that a person loves someone so dearly even after she has passed. For Japanese literature, it´s very common to find that kind of story.
Also, what about the job classes, again?
We see main couples in FFIV, FFVI, FFVII (haha
), FFVIII, FFIX, FFX and X-2, FFXII, FFXIII, and FF: Versus XIII.
Cecil, Locke, Cloud, Squall, Zidane, Tidus, Vaan, Snow and Noctis are shown as high physical fighters. They complement the heroine with their personality and their clothes.
Rosa, Celes, Aerith, Rinoa, Garnet, Yuna, Penelo, and Stella are shown as high magical fighters (mostly white mages, excluding Serah, who isn´t a fighter at all), being very feminine and affectionate to the hero.
Cecil, Locke, Cloud, Squall, Snow and Noctis are shown wearing a dark type of clothes, mostly black. Zidane for example wears blue, but he complements with this Garnets yellow clothing. Tidus complements with his yellow-black Yunas blue-white clothing, too. The heroines are typically shown in white clothing, Rosa in white-gold, Celes in tope (alternatively white), Aerith in red-rosé, Rinoa in blue, Penelo in brown, Serah in white-rosé, and Stella in white.
Furthermore, we can always see a bright, optimistic and cheerful person (Rosa, Locke, Aerith, Rinoa, Zidane, Tidus, Vaan, Serah, and Stella) being in love with a more introvertet, shy and pessimistic person (Cecil, Celes, Cloud, Squall, Garnet, Yuna, Penelo, Snow and Noctis).
I think it´s hardly to deny that Aerith fits very well in this. Also, I think Cloud showing so much affection for Aerith indicates that he cares about her very much.