Why Jonny Quest (yes, his name was always spelled "Jonny" "did left" CN in '96 was to make room for Real Adventures (which I have a foggy memory of, considering I was a toddler at the time it aired). They still show this on Boomerang sometimes, usually during their "Questmas" and "A Hadji New Year" marathons (they didn't do Questmas in 2006, or Hadji New Year on 1/1/2007).
Venture Brothers is NOTHING like this... Venture Bros. is just a parody of a few different toons, this included.
There was another series of this called "The Real Adventures of Johnny Quest" that involved 3D computer technology for both the intro and "Quest World" (a giant Virtual Reality system created by Johnny's dad)