Last years' latest and greatest are already vintage. The manufacturers are so caught up in making obsolete anything that works well, that you are always behind the curve with these bikes. You have a "vintage" bike the year after you buy it. 26, 29er, 27.5er, 27 plus, 29 plus, 26 fat...(the next best "improvement" will be ""26-plus") QR axles, Maxle, Boost, super-boost, slack seat and head angles, steep seat and head angles, short chainstays, long ones, long offset forks, short ones, threaded BB's, press-fit BB's, 1" headsets, 1.125" headsets, 1.5" headsets, tapered headsets, triple rings, single rings, double rings, 7-spd, 8-spd, 9-spd, 12-spd, single-speed, fat, semi-fat, Plus, shoulder-width bars, 800mm bars, no remote levers, all remote levers, droppers, no dropper, toe-clips, clipless, platforms, combo clipless/platform, too little, too much, it never ends. All of it conceived so you cannot swap new parts on to your old frame that you love so much. Today you are forced to buy all new or you are just not "with it". I am one who resists this madness. Icannot tell the difference between a Fox 32mm fork or a 36mm fork, nor can I tell that a maxle or Boost rear axle makes any difference in stiffness. I call BS on all of it.....
In terms of real classics, I think they were the 1st gen MTB's from the 1st makers from the 80's and 90's...Ritchey, Specialized, Ibis, Klein, Litespeed, Moots, and others I may have missed. 26"/hardtail/3x....quick release 135mm rear axles and threaded BB's with 1st-gen Shimano XTR. My 2cents here being an MTB rider. .