Ack... I had a big post for this, and obviously never sent it. Basically said that most traditional film genres don't do a very good job of describing anime, and the current hybrids that anidb and ANN have are a poor solution. So, if you were going to categorise anirec, I'd suggest rather than having "action, drama... shounen... mecha" you draw up something closer to a 'content' list, and use that. Certainly being able to click on 'harem' as a topic, and memorise the animes as not-to-watch would help me.