The former Spice Girls manager says the programme has lost its "negativity" and is concentrating on relating to the contestants since the acid-tongued music mogul quite his judging role.
He said: "We wanted to lose the negativity and be more motivational. We understand this show's success is based entirely on the authentic Journey of real people with a passion and a dream, no gimmicks, no spin, no smoke and Mirrors.
"The best surprise about this new 'Idol' season is the positivity and energy."
The 50-year-old producer also revealed how everyone involved in the show is taking more pride in their work since Cowell left.
He explained to the Daily Mirror newspaper: "All the producers, Editors and crew have taken a new pride in the show. Each person focused on making everything they do better."
Cowell - who produces rival reality talent show 'The X Factor' - left 'American Idol' last year and Fuller says his new judging panel of Jennifer Lopez, Randy Jackson and Aerosmith frontman Steven Tyler are much more sympathetic towards the aspiring hopefuls who audition.
He said: "The addition of Steven Tyler and Jennifer Lopez, real stars who also shared that dream, has brought a new level of understanding and empathy to the show.
"They can identify with each and every one of those contestants and what it really means to have a dream."
Fuller also praised the show's new mentor Jimmy Iovine, calling him: "Probably the world's most brilliant music executive and producer".
Cowell and Fuller legally battled over the similar formats of their TV shows in 2005 and eventually settled with an out-of-court agreement.