Bhagavad Gita, Chapter 18, Verse 69

Nor among men is there any who does dearer service to Me, nor shall there be another on earth dearer to Me, than he.

A real, superlative claim is made here directly, nothing described as coming close to this particular service.

Krishna doesn't rank this alongside other good deeds, he names it as uniquely, maximally dear. Real emphasis is placed on teaching this knowledge as the highest form of service available.