I love this thread. When it comes to pairing, this is how I see it:
Age- age gaps don't bother me, unless it turns into something blatantly pedophilic and sexual.
Gender- I don't care if it is hetero, homo, or otherwise, as long as it isn't something out of character
"Romance factor"- Pairings don't need to be incredibly lovey-dovey. Seriously. Keep 'em in character. Also, I'm usually against sexual relationship things. Most series I'm into don't need to take things that far (Kingdom Hearts, for example!)
Alternate Universes- AUs are cute and funny for things like webcomics, but if you really want to write a good fanfic, you need to stick to your character's regular universe. Well, you CAN pull off a good AU, but in order to do so it has to break away from the normal cliches and be something that is beneficial to your story's point. I'm sure most people make AUs to pull of a pairing (hell, I'm guilty of doing so) but if that's all it is going to be, it is likely it won't be good.
My biggest problems with pairings, especially in the Kingdom Hearts fandom, is that many people seem to value "love" over friendship. Someone tell me what I'm missing or something, because I don't understand. In a sense, friendship IS love (sort of). Think about it. When you've got true friends, ones that come to your house without even calling in advance, the ones that playfully jab you with insults ("What's up, hoe?" [i seriously respond to this]) the ones that listen to you harp on about Homestuck, Kingdom Hearts, and Harry Potter, the ones that embrace your weirdness (or maybe it's just me...?), they're like family to you. I don't know about you guys, but I love my family. Even if you don't, if you ever want to marry someone, you are wanting to become one with their family. But let's back up for a minute.
Just because someone's a friend, family member, or "soulmate" to you doesn't mean that one relationship is not as important as the others. I'm a very shy person, but even I know that you need friends. Well, technically you don't, but you need friends as much as you need a family and a "deeper" form of love. You will not physically die if you a friendless, familyless, and loveless. However, you must realize that valuing one aspect over another leads to imbalance.
That being said, friendship is beautiful. I absolutely love Axel and Roxas as separate characters. By that, I mean that I love each of their personalities, goals, and (though with Axel it is usually unclear) motivations. Their friendship is one of the most beautiful things in the series, in my opinion. Seriously. Also, if you ever have the time, go back and play KH1. For some reason, I get all teary with the Sora-Donald-Goofy trio. It's simple beautiful. You don't have to force anything into place, because it is already there: friendship. I cried to first time I played KH1 when Sora became a heartless. Why? Does anyone remember how Donald ran to him ("Sora! Sora! Come back, Sora!!!) while an instrumental of "Simple and Clean" played in the background? (Okay, when I watched it the 2nd and 3rd time, I realized it wasn't as dramatic as I remember, but everything I just said actually occurs in the video... plus, it is still amazing!) Donald and Sora went from fighting and arguing to the best of friends. I don't understand how friendships like this can be minimized when compared with shipping.
Also, shipping causes fights. I "lightly ship". That means that I ship for fun, not seriousness. I don't even have a desired shipping for this franchise, I think. (None come to mind right now.) Why does it have to be something that causes fights? Can't we all just sit on the clock tower and eat some sea-salt icecream? Who cares how everyone will end up getting paired? It's not like they're going to hate each other for it! If (by some grace of God) Sora x Riku ends up canon, I'm 99% positive Kairi wouldn't hate either of them for it. But please, let's not start fighting here.
I'm sorry about all the blabbing, so I'll end it here. I just needed to get things off of my chest. In short, friendship is wonderful, pairings shouldn't be many just to demote friendships, and shipping shouldn't be something that people fight over. I just wish more people felt this way.