Why is the carbon monoxide triple bond stronger than the nitrogen-nitrogen triple bond?
I agree in part with Mithoron and MaxW's comments: these are different molecules, not even sharing a mutual atom (e.g. C-O vs C-C), so direct comparison is restricted.

However, Pauling's concept of electronegativity does explain why, in general, the heteronuclear A-B bond is stronger than the average of the homonuclear A-A and B-B bonds. the difference in the electronegativity of the two atoms in the bond lend a somewhat ionic character to the bond, strengthening it.