1st fallacy(LOL doesn't that sound impressive?)-
-Aerith only loved the "Zack" in Cloud.
Not true. I can see how people would think that...but, it's not the case at all. Aerith was ATTRACTED to Cloud because of his resemblance to Zack, her first love. HOWEVER, along the course of the game, she begins to realize that Cloud is different, and she still loves him. Aerith is the first one to see signs of the "real" Cloud and try to bring them out. Example, their date at the Gold Saucer...Aerith says something along the lines of...
"At first it bothered me how alike you were...but you're different...I want to meet you, Cloud..."
It was something like that, give or take a few words. This line proves that she really loved HIM, not the resemblance he bore to Zack. Now, it is debatable whether or not he loved her(I think he did, but that's an opinion), but it's true that she really cared for him, as Cloud, not Zack. :)
-Aerith broke up Tifa and Cloud!
Er...not really. Tifa and Cloud were never TOGETHER in the first place when Aerith came along and Tifa even told Aerith that she and Cloud were nothing more than friends. So...how exactly did she break them up again? Whether or not Tifa and Cloud get together in the end is debatable, but in the beginning they were NOT together.
-Cloud can never love Aerith! She's DEAD!
Let me get this straight before I continue... JUST BECAUSE AERITH DIES DOES NOT MEAN CLOUD CAN'T LOVE HER!!! *ahem* Sorry, just had to get that out...now... Who says you can't continue to love someone after they die? Hm? It happens to be quite common. Though some lovers DO move on and find someone new, it does NOT mean they STOP loving the one that passes away. It happens to be quite possible that a)the lover still holds his/her loved one in their heart, but is ready to move on, and while they never forget or stop loving their lost love, they are able to move on and love anew, or b) the lover holds his/her lost lover in their heart forever and awaits the day they can be together once again. I say this because I firmly believe that Cloud DID love Aerith. That does NOT mean he never loved Tifa as well, it just supports my theory that he cared deeply for both...