Why is N2 enthalpy zero, entropy 191.5, yet G is listed as zero and not [-T*0.1915]?
Enthalpies of formation and Free energies of formation are expressed relative to the standard state of 25 C and 1 bar.  So, in the standard state, they are taken to be zero.  The entropy value you cited is the absolute entropy, relative to absolute zero.  If you wanted the entropy of formation of nitrogen relative to the standard state of 25C and 1 bar, that would be 0.