I don't know, these games are still fun, but Red Ball 2 was the best. The physics haven't quite seemed right since, and the levels just seem less inventive and interesting.
It was pretty fun... up until I realised that it was pushing 'Intelligent' Design nonsense to schoolchildren. It puts up a mask of science, but promotes some very unscientific ideas. Keep this as far away from the classroom as possible.
Fixed sorry about that