I would say 'vintage' is really any 'old' gear. To put a finer point on it, I'd go with 25 years, as that is the definition of "antique" for automobiles in CT and NY (and when you get the better rates!)
I think any piece of equipment that shines in many areas can be labeled as "classic". A 1985 BMW is an antique; however a 1995 M3 LTW is a classic (for example)
Generally a classic piece is one that had favorable reviews, and therefore a good purchase base, and has also stood the test of time with continued demand.
Conversely, a Tice clock is a piece of gear that is vintage (due to age) but truly a horrible piece of equipment that did not do what it said it did. So, just because it is 'vintage' does not mean it is good. And further, 'good' is so subjective that I always try to have several reviewer's opinions before I even go to the trouble to audition a piece of gear, because of this detail.