Some are; some are not.
.edu is not necessarily better than some .com. If the link is from a university's law school resources pages and links to your site on law books, this may be more valuable, than a student's page with a lot of links to and discussions about what beer is best for getting drunk the quickest.
The Google algorithm does consider the trust factor on domain names. Because just anyone of the street can't get on GoDaddy and buy example.edu, it will automatically get a trust boost.
Some discussion of the different values of the .edu can be found at: http://searchengineland.com/explaining-edu-link-value-with-examples-64012