You make some really great points and as much of a fan as I am n Cloud x Tifa, I still have to say that his love interest was Aeris.
Based on what exactly?

I only got the vibe that Tifa was his friend, and even in Advent Children when they were "living" together in the bar, Cloud wasn't there most of the time.
Cloud wasn't there in AC/C because he had left due to his guilt. Look at the quotes I posted. This will give you a better understanding of where Cloud's head was at. I'd also advice you to read Case of Tifa as it explains when Cloud left.

Also in the beginning of CoT it's clear that Cloud wants Tifa by his side and it's "different from before."
Quote Originally Posted by Case of Tifa
“Cloud, you’re smiling.”

“I am?”

“Yeah.”

“It all starts now. A new…”

Cloud looked for the right words.

“A new life.”

“I’m going to live. I think that’s the only way I can be forgiven. All sorts of things… happened.”

“That’s right…”

“But when I think about how many times I’ve thought about how I was going to start a new life, it’s funny.”

“Why?”

“Because I’ve always failed everything.”

“That’s not funny.”

“After this … I think I’ll be okay.”

Cloud was silent for a long time before he spoke again.

“Because I have you this time.”

“You’ve always had me.”

“What I mean is kind of different,” Cloud answered with another smile.
Cloud is talking about having Tifa by his side in a way that's different than before. Keep in mind they shared their mutual feelings for one another under the highwind and it wouldn't make sense for them to be establishing a friendship they already had...

As for him being gone in Advent Children... well yeah... we established that he had left at that point. He ran away so to speak, and it wasn't because of Aerith, it was because of Geostigma as stated more than once in the 10th Anniversary Ultimania:
Quote Originally Posted by 10th Anniversary Ultimania
· AC – Midgar
Because he contracted Geostigma, he left Tifa and the children, and began living in the Slum church.
---------------
Now running a delivery business while helping out Tifa with the newly opened “Seventh Heaven” bar, Cloud, Tifa, Marlene and Denzel lived together like a family. However, when Cloud contracts Geostigma he disappears.
Not only that but Cloud specifically states in Advent Children complete that the reason he left was because he felt he couldn't care for anyone let alone himself. So that's why Cloud wasn't in the 7th heaven very often in AC/C. Geostigma.

Even after all that happened, through-out their child hood, and through Nibelhiem burning, and the game of Final Fantasy 7 itself, Tifa was never more that his one true and closest friend.
I disagree and if you look at the texts I think you would too.

You have her and Cloud having memories together related to their future, Cloud and Tifa belonging together (see above), their hearts calling out to each other (in the lifestream), his opening his heart only to her, her being the important woman to him and mother of the family they were forming (See above), him being the father in Tifa's eyes (case of Tifa), Cloud being Tifa's lover interest (Ultmania Omega), the risque implication of the night under the highwind, and most important them sharing their feelings for each other. Have you ever known that statement to be non romantic?

I don't really think Cloud was in love either, but I think he had more of a romantic relationship with Aeris than he ever did with Tifa.
Again, what are you basing this on? I'd like to hear it.

But Cloud also was the type to not show his true feelings that much. Making this argument really pains me though, cause I was never to fond of AeriaxCloud shizz.
I like the pairing as fanon but when you have all the information I listed above plus Nojima speaking of love, marriage and family in the context of Cloud and Tifa, I think it's obvious who the canon couple is.

In the original 1997 game, it appeared that Cloud's love interest was somewhere between "completely ambiguous" and "kinda leaning toward Aeris."
Is anyone going to tell me why they say this XD

And could you please tell me what retcons you're referring to? I did not see any, but yes I agree SoS's essay on the subject was excellent. He really knows his stuff.

But since 2005 or whatever with the coming of the FFVII: Retcon Edition series, there have been major, if not overwhelming implications towards Tifa being Cloud's love interest.
I concur.
I look forward to hearing back from you and Melissaur.