Bhagavad Gita is the original, the stem from which originated all branches. The sermon of Bhagavad Gita by Lord Krishna forms core of spirituality. Initially advent Lord Krishna, about 1500 years earlier to coming of Jesus Christ! A few centuries later followed Prophet Mohammed.
In Hinduism seekers in hundreds succeeded reaching state of enlightenment whereas in the West only Jesus Christ and Prophet Mohammed gained enlightenment. The reason for this being, spirituality is not well understood in the West. None in West tries to become one like Jesus Christ or Prophet Mohammed.
In Hinduism serious seekers followed teachings of Lord Krishna and down below only to assimilate pearls of jnana wisdom contained in sacred texts like Bhagavad Gita and Upanishads (independent spiritual treatises). When they successfully reached state of enlightenment none in Hinduism tried to develop an independent following. This was not necessitated at all.
On the contrary in West after coming of Jesus Christ developed Christianity. With coming of Prophet Mohammed evolved Islamic Dharma.
Everything contained in Bhagavad Gita and Quran also exists in Bhagavad Gita. But everything contained in Bhagavad Gita is not contained in Bible and Quran. Whatever precepts of spirituality were understood by Jesus Christ they are incorporated in Bible. Whatever was the understanding of Prophet Mohammed, accordingly the teachings contained in Quran!
In present times none can reach God, gain state of enlightenment indulging in Bible or Quran. In present times enlightenment can be gained only by indulgence in Bhagavad Gita alone.
The best part of Bhagavad Gita is, though it is part of Hinduism scriptures it has universal appeal. Any human being even while following ones religion can indulge in teachings of Bhagavad Gita to reach state of enlightenment. One even need not convert to Hinduism religion.
The teachings of Bhagavad Gita relate to spirituality not religion. Whereas teachings of Bible and Quran as understood by most in present times relate to religious aspect of life than spirituality.
State of enlightenment, God in present times is reached following spirituality never religion.