I read on Wiki that it was in development since 1992 ._. I think that was when the anime series was still on air xD
Here's what Wiki has to say.
The film had been in development since 1992, changing writers and directors until producer Joel Silver and the Wachowski brothers collaborated to begin production on Speed Racer as a family film so the directors could reach a wider audience. Actor Emile Hirsch was cast as Speed, the hero of the animated series, and Christina Ricci portrays Speed's girlfriend, Trixie. Speed Racer was produced in Germany at Babelsberg Studios, where filming took place entirely against green screen.
I've never seen any films done by Germans, and it saying that they are against green screen (that's used for special effects, etc) perhaps that's why it looks a little bad?