Over the weekend, a petition surfaced that called for Grammy policy changes. The Change.org item argued retail albums should not be the only projects considered for awards, as there have been many important projects released for free over the last few years that were not eligible due to way they were released. Anyone who follows rap knows that the mixtape is often better than the album, and free releases have made up some of the more exciting statements in the genre over the last few years.

In support of the petition, we've put together a few groundbreaking mixtapes reaching all the way back to 2002. Of course, there are far more mixtapes deserving of recognition than the ones listed, but it's safe to say that these projects made just as much of an impact as many of the albums nominated each year at the awards.

Click through to take a look at our picks, and let us know which other projects should be rewarded as well.