Of course 'classic' is as defined by the media BiTD, coupled with one's own interpretation spun in with peer pressure today
Tomac's Raleigh DT with a disc drive in my opinion is a classic, because it's a pure icon of the era.
Media coverage everywhere, ridden by Tomac and you're unlikely to have one. Are the 'replicas' classic nowadays or are they still just copies of a classic, that is open to debate imho.
at the other end of the scale .. Orange Clockworks, ridden by the general masses often the first step into a real mountain biking for many a Brit or at least soeen as such. Though is it the clockwork that is the classic or just the orange/white banding of orange bikes ?
Are top end frames classics ?
For example my 1991 RM Altitude.
It's the first year of their race coloured bike riding the altitude name, shown in many interviews and by the teams at events. Stamped with a RM frame number..
But it's just a steel frame made by decent builders from high end prestige tubing like many others of that era.
But I know what is retro and what is vintage to me, I know what is a classic to me.
MTB
Retro, circa 1992
Vinatage, the stuff before I was really into MTB
Classics, just the bikes to me that stood out as iconic for the era, or brings out fond memories of the era. (ignoring peer pressure preferably)
Though one's memories are different, we where much more isolated from one another to spread opinions, kult status of equipment or even what bike where available to you (BiTD of circa 1992)