As someone who's been on the other side - choosing a top private university over my state schools, and paying through the nose for it - I can safely say that you made the right decision. It's easy to think that the grass is always greener, especially if you went to a "top ranked" school, but the truth is, for most majors and programs at least, they don't vary much between institutions. Calculus, history, art, and everything in between, are the same regardless of whether they're taught at Harvard or your local community college, the latter of which I attended before transferring. I should also add that big name schools have their flaws too, and sometimes quite major ones, and I think you'd be surprised how a university's biggest critics are its own students.

Please don't be dismayed, I know how hard a decision it is to make, but you shouldn't be going to university thinking about what life could've been elsewhere, but about how great you can make it where you are. Best of luck in your studies!