It would be great if you could let users indicate preferences between answers so that you could produce an ordered graph of which answers are better than others

It would be great if you could let users indicate preferences between answers so that you could produce an ordered graph of which answers are better than others. I'm thinking of something similar to the less wrong textbook recommendations[1] with it's rules: 1. Post the title of your favorite textbook on a given subject. 2. You must have read at least two other textbooks on that same subject. 3. You must briefly name the other books you've read on the subject and explain why you think your chosen textbook is superior to them. Rules #2 and #3 are to protect against recommending a bad book that only seems impressive because it's the only book you've read on the subject. AFTER EDIT: I'm thinking this would be particularly useful if you've narrowed your choice down to a few options and wanted to see comparisons between those options. [1] http://lesswrong.com/lw/3gu/the_best_textbooks_on_every_subject/ http://lesswrong.com/lw/3gu/the_best_textbooks_on_every_subj...