Hinduism is the oldest religion existing on mother earth. Even before Hinduism came to be called a religion, a way of life it was termed Sanatana Dharma, an eternal Dharma existing from times immemorial, from the beginning of life.
The primary principles of life nay Hinduism came into existence with Vedas, the first words of God revealed to mankind. In all there are four Vedas… Rig Veda, Sama Veda, Yajur Veda and Atharva Veda. All Vedas dealt with different fields of spirituality and life.
As jnana wisdom contained in Vedas was voluminous, beyond masses to understand and digest God Almighty bestowed on mankind advent of Lord Krishna, an avatar… saviour messiah of his era. With advent of Lord Krishna the requisite wisdom necessitated for mankind to reach state of enlightenment precipitated in form of Bhagavad Gita.
After advent of Lord Krishna the need for mankind to indulge in Vedas did not exist. Everything that was necessary to reach God in our lifetime existed in teachings of Bhagavad Gita.
From all angles Lord Krishna, his entire teachings contained in Bhagavad Gita can be considered as start of Hinduism religion. Bhagavad Gita deals only with the spiritual aspect of life. Nothing related to religion (rituals) exists in Bhagavad Gita.
About 1000 years later to coming of Lord Krishna advent Mahavira, 24th Tirthankara of Jainism. Rightly advent of Mahavira should be considered the start of Jainism. The initial 23 Tirthankaras in their lifetime succeeded in reaching cosmic end of life, becoming a pure soul atman at the end of spiritual journey. But the jnana wisdom gained by these 23 enlightened Tirthankaras remained confined to them and did not percolate to the masses.
With coming of Mahavira the entire philosophy of Jainism finally reached the masses, prime reason why in present times followers of Jainism gave more precedence to Mahavira than other Tirthankaras (enlightened ones).
Hinduism primarily precipitated to the masses with advent of Lord Krishna and Jainism during times of Mahavira. A difference of 1000 years speaks of itself. Everything contained in scriptures of Hinduism also exists in Bhagavad Gita but Jainism scriptures do not contain everything of Bhagavad Gita. The sacred text of Bhagavad Gita forms summum bonum of spirituality. The knower of Bhagavad Gita finally becomes knower of all, reaches God in one’s lifetime.
Without delving into which religion came earlier, we must logically enlighten ourselves about jnana wisdom contained in both the religions.
As the cosmic goal of human journey was reaching state of enlightenment, as a human being it is in our interest that we indulged in spirituality contained in Bhagavad Gita to reach 8.4 millionth manifestation, finally becoming a pure soul atman at the end of cosmic journey.
Born in a Jain family from six years of age I followed teachings of Lord Krishna in Bhagavad Gita. Everything came from within. I never despised teachings of Jainism ever yet I believe more in teachings of Lord Krishna contained in Bhagavad Gita. This was for the only reason that indulging in Bhagavad Gita I could liberate self from cycle of life and death forever.
In my spiritual travail I never rejected any religion. Whatever little I could gather from any religion, I accepted it with reverence. If I met someone possessing jnana wisdom worth knowing then I treated one like my guru. Instead of shunning people and religions, I took the best of all. In my zest to reach God in present life time I tried to reach the underlying unity of all religions and people. I was never proved wrong in my surmise.
Summarizing it all both the religions Hinduism and Jainism are worth emulating. Whatever best we could have from both should be accepted with folded hands. After all it was only grace of God Almighty that we were born a human being, the highest manifest stage in cosmic life cycle. How could we question something created by god?