Definitions can vary widely, but my definition of a class leader is a model that, while not best in every area, stands out from its competitors from an overall perspective of performance, driving dynamics, styling, quality, reliability and value. They may even be below average in one category, if they excell in the others. A few of many examples, in automotive history, would be the Models T and A Fords, the Buick Century of the '30s and mid-'50s, the '49 Ford and Mercury, '49 Chevy, Olds and Cadillac, the Hudson Hornet of the late '40s through about '51, the '53 Studebaker, the VW Beetle, the '55 Chevy, '55 Chrysler New Yorker and 300, the late '50s - early '60s Rambler, the '65 Mustang, the down sized '77 GM large bodies, the Camrys and Accords of the '80s - mid '90s, the '88 - around '96 Maxima, the '99 - '08 Acura TL, the second and third generation Preludes, and first through third generation Integras, the '86 - late '80s Mercedes E-Class, the various BMW 2002 and various 3-Series. I'll stop there, acknowledging that I probably missed a lot of great examples.
You may agree or disagree with my definition and examples of class-leading. Please share your knowledge and opinions.