Electronegativity of carbon remains the same in all compounds mentioned in the question, that is around 2.5. However, since in alkenes and alkynes, carbon has electrons in the pi orbitals, which are less available for sharing, so the electron releasing capability of carbon in alkenes and alkynes is slighly less than alkanes. So it cannot be order of electronegativity, but the electron releasing ability of carbon in the above compounds is in the order - 

ALKANE > ALKENE > ALKYNE