Serious question here. What do you look for when watching a Maple vid?

I look for a collaberation of things in movies. I dislike movies that are overwhelmed with useless special effects that do nothing more than cause my head to spin watching the frame make five circles before coming back into focus. That's not to say, however, that special effects are not a nice addition in videos. If used affectively to make a transition in a clip and the transition looks clean then, by all means, go for it.

Music. Going along with what everyone else has said, don't show me a video of Time Temple with some obnoxious death metal. Make sure that it is befitting of the overall mood and tone of the video. Music in many ways is key to keeping viewers watching the movie. Avoid using songs that are frequently used - if I hear "Until the End" by Breaking Benjamin I automatically give the video a "1" rating and stop watching it.

Content is obviously the most important. Uploading videos of you killing a boss that has been implemented into movies a million times over is all good and well, but not enough that I'm going to sit and watch every single last godawful one. Mix it up. Make it a mishmosh of all sorts of different in game content. Don't be afraid to try something out of the norm.

Have some fun with it and invest the time and effort to make it look good.