Now that gay marriage is legal, this is the most important issue for millennials.
No, it isn't. College affordability and stable growth/job opportunities are. Cannabis legalization is just a "yea okay" issue.
P.S. Climate change also more important
Exactly. I'm more worried about getting through college with as little debt as possible, entering a stable economy and job market in ~four years, and living in a society which cares about the environment. Sure, I'd like to see marijuana legalized, but it's not high up on my priority list.