#2 Alex Barros
In 1986 at the age of just 15, Brazilian Alex Barros made his 80cc class debut. In 1990, he became the youngest rider at the time to participate in the 500cc class. He has had wins across 500 cc and MotoGP classes. He also has won a Superbike World Championship race in 2006. Alex started in 245 MotoGP races.
#1 Valentino Rossi
The only person in Motor-racing history to win Championships across 4 different classes, Italian legend #46 Valentino 'The Doctor' Rossi has won Championships in 125cc, 250cc, 500cc and MotoGP classes. The winner of 7 MotoGP Championships, 89 race victories and 196 podium finishes, Rossi is by far the most popular rider that the sport has ever had. Approaching 40 hasn't deterred him from pursuing his dream of winning the 8th Championship. As of the 2018 Thailand Grand Prix, Rossi has 319 race starts.