C F G occour major naturally in the chromatic scale eg. 5 semitones then 4 to move up 3 white notes.

D E A B occours minor naturally in chromatic scale eg. 4 semitones then 4 to move up 3 white notes.

The minor chords can turn more major (whilst using the black notes) by cutting out the middle note.
There is an exception to this rule, which is the note B, its a bit gay.
Because these are not naturally occouring in western music (a listener can't tell if its major or minor), They should be used for 2 / timesig

Blues Riff sounds good because its the only way of moving a note (in this case G) two semitones without moving the base note.

Moving the G down two semitones sounds like a shitty chord, but when broken down, it sounds really good. Also, when made into chords, they are all major.