My list of all-timers:
1, Every 1969 model Yamaha, from RT1-DT1-CT1-AT1-LT1-HT1... etc a bike for everybody at every skill level
2, Suzuki TM125, not a world beater but they were cheap to buy, reliable, cheap to maintain and an easy start for a budding racer
3, Suzuki 1977 RM-B series all the foibles of the A models sorted they were a screaming yellow menace to anyone not on one
4, Yamaha YZ250/465G Kings of the hill albeit for 1 year
5, Maico 490 mega2, enough said
6, Suzuki Full-Floaters best rear end ever
7, Yamaha TT250/350 1986 Honda XR's big wake up call (wasn't it amazing to see how reliable they became after the TT's came out)
8, The Chinese pitboss mini
, Yes we bag them and hate them but they took a cynical youth off their skateboards/bmx's/drugs and put them back on two motorised wheels. Sure most of them thrashed trashed and thrown away but if we get another Chad Reed or Casey Stoner out of it then they were a good thing, they certainly stung the Japanese into providing a more diverse and up to date range of entry level bikes than had been available for years but sadly never will we see the likes of 1969 again