ok, putting bhagavad gita aside, lets look at what others sastra's say...
In the Atharva Veda (Gopala-tapani Upanishad 1.24) it is said, yo brahmanam vidadhati purvam yo vai vedams ca gapayati sma krishnah: “It was Krishna who in the beginning instructed Brahma in Vedic knowledge and who disseminated Vedic knowledge in the past.” Then again the Narayana Upanishad (1) says, atha purusho ha vai narayano ’kamayata prajah srjeyeti: “Then the Supreme Personality Narayana desired to create living entities.” The Upanishad continues, narayanad brahma jayate, narayanad prajapatih prajayate, narayanad indro jayate, narayanad astau vasavo jayante, narayanad ekadasa rudra jayante, narayanad dvadasadityah: “From Narayana, Brahma is born, and from Narayana the patriarchs are also born. From Narayana, Indra is born, from Narayana the eight Vasus are born, from Narayana the eleven Rudras are born, from Narayana the twelve Adityas are born.” This Narayana is an expansion of Krishna.
It is said in the same Vedas, brahmanyo devaki-putrah: “The son of Devaki, Krishna, is the Supreme Personality.”
(Narayana Upanishad 4) Then it is said, eko vai narayana asin na brahma na isano napo nagni-samau neme dyav-aprithivi na nakshatrani na suryah: “In the beginning of the creation there was only the Supreme Personality Narayana. There was no Brahma, no Shiva, no water, no fire, no moon, no stars in the sky, no sun.” (Maha Upanishad 1) In the Maha Upanishad it is also said that Lord Shiva was born from the forehead of the Supreme Lord. Thus the Vedas say that it is the Supreme Lord, the creator of Brahma and Shiva, who is to be worshiped.
narayanah paro devas
tasmaj jatas caturmukhah
tasmad rudro ’bhavad devah
sa ca sarva-jnatam gatah
“Narayana is the Supreme Personality of Godhead, and from Him Brahma was born, from whom Shiva was born.”
ISVARAH PARAMAH KRSNA
ANADIR ADIR GOVINDAH
Krsna who is known as Govinda is the Supreme Godhead. He has an eternal blissful spiritual body. He is the origin of all. He has no other origin and He is the prime cause of all causes.-Brahma Samhita