If you think about it, a lot of the time, anime we watch tends to be awesome at first, but then later, we tend to forget about it, or it loses its appeal, or we wizen up, what have you. If it's shit, it usually stays shit.
Mediocrity, however. We watch something that was alright, decent, nothing special. Then we go back for whatever reason, and it's as if it's under a whole new light.