With his career now in the books, I think it's clear Kirk Cousins finished as the greatest quarterback in school history.
No, he's not the most prolific. He doesn't have national championships nor a Rose Bowl appearance (but damn, was he close twice). It's hard to compare eras in football. Cousins throws more passes per season than a lot of guys did in their careers during MSU's glory years of the 50s and 60s. From a physical standpoint, it's quite obvious Cousins is better than those guys.
And everything Cousins does off the playing field certainly plays a factor, along with all the on-the-field records.
Here is my post for MLive making the case for Cousins as the greatest quarterback in Spartan history.