In the second last lap of the race, Rossi managed to get past Ducati's Andrea Dovizioso and hold him off for his 70th career win.
The 36-year-old rated is victory right up there with the best of his career.
"This was one of the best victories for me," Rossi told MotoGP's website.
"The bike was fantastic, I never gave up but it was a real fight with the Ducatis and the Hondas who were really strong."
Rossi feels that Dovizioso and Ducati team-mate Andrea Iannone, who completed the podium, will challenge Japanese outfits Movistar Yamaha and Repsol Honda this year.
The Italian added that he believes that he can race for another four years before retiring.
"I feel good, I have good motivation and I like my job because it is also my passion, like all the guys here. For me, if you live a good life, good training, you can ride at the top until 40-years-old," Rossi said, according to crash.net.
"What makes the difference is more the motivation and the concentration.
"So I am so happy because Marc is behind, which is very important for the championship, but this year I think there will be six instead of four [title challengers], because the two Ducatis are very strong and they are riding in a good way, so it will be very interesting," he added.