When I think of something being 'underrated' I usually mean it isn't given a chance. I might refer to an anime I love by saying "it's so underrated." I mean people don't notice it, haven't heard of it, or don't even try it because what they have heard isn't glowing and popular enough - generally because they're too busy checking out the 'overrated' anime. A lot of the time the only difference between over and under-rated is the promotion. People don't download (or watch new anime) because it's good, they do it because they *heard* it was good.
So...it's all about advertisement and the fanbase. If I have a vid where all of the few people who watched and reviewed it did so with glowing praise, but they failed to "tell a friend" then it's an underrated video. If I happen to agree with them, that just means I'm more likely to pimp it in this thread. I don't have to think the video is good for it to be underrated. For me, it's all about the vids that aren't given a chance by casual browsers, but are liked by the ones who bother to watch it.
That said, I don't want to argue about what 'underrated' means to a dictionary or a computer. I'm going by the definition I ascribe to. By my definition, there's no such thing as over or under rated from an objective view point. Opinions determine ratings, so it's subjective from the start, whether it ends up over or under.
/end disclaimer
I don't know what my most underrated vid is. I tend to look at my own vids according to anime. For Sailor Moon, my 'Enduring Love' vid would be underrated, while 'Star Crossed' is way overrated. For YYH, 'Cry for Me' is way overrated while 'Living the Dream' is underrated. It's funny. If I compare the overrated vids I get when I think about this thread, to the top star-scoring vids I would get for that thread, I get the same thing. The most simplistic videos I make get the downloads and praise, especially when they use overused and popular anime sources. It's a wonder I haven't made any Linkin Ball Z vids. The more overused the sources and the simpler the editing, the more people like the video. It's mindboggling.
That's not how it's supposed to work.