"He (Alonso) is always at a high level," Villeneuve said at Interlagos, "but what we saw from Alonso in 2012 I have not seen this year. That was second to none -- the best I've seen.
"This year, with the statements (made by Alonso) about Ferrari and everything, there was too much negative energy," he added.
Next year, Alonso will be paired at Ferrari with a new teammate.
"(How will he fare) with (Kimi) Raikkonen?" Villeneuve said. "The Lotus is a great car this year. All I'll say is that Alonso would have won this year's title in that Lotus."
Alonso joined Ferrari in 2010 but, although he has come close, he is yet to add to his tally of two world titles, won at Renault seven years ago.
The Spaniard has had an often tense relationship with Ferrari this year, but despite flirtations with Red Bull and McLaren, he is staying put for 2014.
"You have no other choice than to be patient," Alonso told the Brazilian newspaper O Estado de S.Paulo newspaper at Interlagos.
"Sometimes it's frustrating. For days and days. But I have to use this anger in a good way, to work harder and to win again," he insisted.
Meanwhile, while Alonso's comments about Sebastian Vettel might often sound uncomplimentary, the 32-year-old insists the Red Bull driver deserves his success.
"With the same car, Webber was not able to win any titles," Alonso said. "It's clear that Sebastian deserves it."