Wayne Rainey was one of the best, too bad his career was cut short. Doohan would of never had as many championships as he did have, and Kevin would of never won his only in 93. Another would be Eddie Lawson he won 3 times with Yamaha and his final one in 1989 on that evil NSR500, needless to say he ran away from Honda the next year. I wonder why? lol
Then before these guys (and before I was born) there was Kenny Roberts Sr. And as TMKIWI said Agostini and Sheene are other names I can't forget either.
As for Rossi he's a legend in MotoGP. He won the 500GP championship in his second year. It also was the final year for the 500s.
But Rossi has said multiple times he'd rather race the 500 2 stroke.