The Spaniard added: "This is the first time that I have got drivers, ex-drivers, teams, fans to say that we have done the best championship. We'll be back as strong in 2013, because it would be harder to be stronger."
Alonso was ahead of Vettel almost throughout the race in Brazil, but apart from a brief period at the start, their respective positions always meant the German was on course to win his third consecutive world title.
Alonso pointed to the Belgian and Japanese Grands Prix as the decisive races in him losing the title.
In both races he retired at the first corner following collisions with a Lotus car.
In Belgium, his Ferrari was hit by the flying Romain Grosjean and in Japan Kimi Raikkonen's front wing hit Alonso's rear tyre and gave him a puncture.
In Japan, Vettel escaped a penalty despite holding Alonso up in qualifying and after the race in Brazil the Spaniard made it clear he had been unhappy with that decision.
"The championship was not lost here," said Alonso. "The championship was lost when Grosjean flew over my head or when Vettel surprisingly only got a reprimand after qualifying in Japan. I have a great feeling after 2012."
"There's been situations during the season that make you think of these three points, but that's the sport. Even though I finished second in the points I have never had such respect and the affection from everybody in the paddock.
He said he felt much better than he did after losing the title to Vettel at the final race of 2010, when he went into the Abu Dhabi Grand Prix 15 points clear of the German but lost out following a major strategy error by Ferrari.
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