Part of it too is how much recognition you crave. I mean, sure, I would love my videos to be hot shit in the AMV world, that'd rock. But that's not why I make AMVs. I make them for the outlet, so I can say "This is my idea, my concept." It's not for the minuscule amount of fame in an internet subculture, it's about my desire and ability to express my ideas.
That's what I think it's about. So to that guy making the 1000th Linkinball Z video, that's awesome man. I hope it comes out exactly how you want it, and I hope you enjoy it and make more. But after that, it comes down to audience, and what audience are you looking for. Someone like myself doesn't really want to watch
yet another one, but I'm sure someone does. Or maybe they made it for their friends, because they all thought it was cool. The video with the blocky compressed version of Sephorith from someone else's video, or the dancing Vash flashing in the corners may have a different objective, which would be to get all the fan boys/girls to scream and clap for their video at the AMV showing of their local con. Hey, if that's what you want, cool. Go for it. I hope you make more people cheer and show up to the AMV contest. I'll be the guy up front grumbling about your video.
Then you got someone like, Beowulf, the arteest

He makes videos to expand the artform

He doesn't really give a shit what you think about his stuff, though he loves you if you like it. That's not why he does it though, he does it for him. You'll see why when his big vid's released. He takes AMVs seriously, which is a good and bad thing. The audience for his kind of video would probably be another AMV creator. His videos aren't really fan favorite material, and he likes it that way.
Eh, I don't know where I'm going with this. I guess I'll just say a few more things. It's important to identify
why you make AMVs, and what kind you like. As for "good" videos, I believe them to be ones that are good technically as well as conceptually. However, concept takes precedence over technical quality. The determination of good and bad videos is up to whichever audience you ask.