Why are the Star Wars Prequels bad?

I'm trying to explain to my brother why they are bad. I've told him everything from the horrible writing, destroying the originals feel (space epic tragedy turned buddy slap stick teenage attitude film) and the horrible CGI. Could someone give me an in depth summary of why these thing are bad?

I'm not saying you can't enjoy the movies. In fact, being a kid who saw these in theaters I enjoy them but I acknowledge there bad.