People confuse loving one person your whole life, and being clingy. Clingy would be if she were bothering Cloud all of the time, hanging on him constantly, and never leaving him alone. Despite what Tifa haters think, Tifa does not nag Cloud. In fact, she is always letting him make his own decisions, and discover things on his own. When she tells him something or offers her advice, it's Cloud's choice to take it in and to follow it. She always pushes Cloud in the right direction, helping him to grow stronger by reaching his own conclusion in the end. All he needs is a push from her every now and again, but he has always had her full support. Retards may confuse this actually very amazingly balanced attitude as being clingy. Cloud is a man who needs his space, and thinking time. Tifa allows him this, but also expresses her worry as well. She lets Cloud come to her, I feel like that's what she really wants. She doesn't want to force him into anything, but let HIM choose HER. And he has, I believe he's already said he'd like to start a life with her, and that everything's okay with her by his side. Not only that, but he actually said that he'd be around to care for her too, by reminding her who she is. Of course, there's always the promise from long ago to protect her from harm. These two have the most amazing balanced up and down relationship I've ever seen in a game.
That's what makes it so special.