One of the main differences between the God of the Bhagavad-Gita (Lord Krishna) and others is that Lord Krishna has already appeared trillions of times and He will continue to appear. Lord Krishna is not an only one show or only one appearance entity.
1.
“Although I am unborn and My transcendental body never deteriorates, and although I am the Lord of all living entities, I still appear in every millennium [every 8.64 billion years] in My original transcendental form.” (Lord Krishna, Bhagavad-Gita 4.6)
There is no word in the English dictionary to describe a period of billions of years and so the closet word millennium is used. In this verse millennium refers to the Sanskrit word ‘Kalpa’, meaning one day of Brahma, which is 8.64 billion years (day and night together). Lord Krishna appears in His original form once in the daytime of Brahma, thus once in every 8.64 billion years.
2.
“.. I Myself appear, millennium after millennium.” (Lord Krishna, Bhagavad-Gita 4.8)
In this verse millennium refers to the the Sanskrit word ‘Yugas’ (Satya, Tetra, Dvarpa, Kali). Lord Krishna appears in every yuga in a particular form. We are currently in the Kali Yuga and He will appear as Lord Kalki at the end of this yuga.
3.
“O son of Kuntī, at the end of the millennium all material manifestations enter into My nature, and at the beginning of another millennium, by My potency, I create them again.” (Lord Krishna, Bhagavad-Gita 9.7)
In this verse ‘millennium’ refers to the Sanskrit word ‘Maha-kalpa’, meaning the lifespan of Lord Brahma, which is 311.040 trillion years. At the end of Maha-kalpa, Lord Krishna in His form as Lord Shiva destroys the universe and then after a gap of 311.040 trillion years, a new creation cycle begins.