Hindus are either Shaivites or Vaishnavites.
Of course, now we worship all, including Budha and Guru Nanak. It would appear that Devi worship was prevalent throughout India, from a much earlier period, involving animal and baby sacrifice, which made Budha preach Ahimsa or nonviolence as a creed. The famous Kali temple of Calcutta is witness to the blood of millions of animals like goats. People used to offer their first baby as sacrifice, to propitiate the deity.
At the Kali temple at Kodungallore, Keralam, thousands of cocks were being sacrificed by wringing their neck, on Ashwathy nakshatram in the month of Kumbh (Feb. 15 to March 14). This practice is now stopped.
In Tamilnadu, Mariamma is the Devi. Every village has a Mariamman covil (temple). Those who believe in Devi cult, believe that she is the source of all Shakthy or Power. All other Gods are her creation. Scientifically, too, mother can give birth, even without man, as in cloning.
I think India is the only country to have Goddess as the supreme power. It is interesting to note that in the West, God is He. In China and in Islam too, this is true. It is only in India, that Goddess or Devi is equally, if not more, powerful than the He Gods, like Shiv or Vishnu. While the influence of the latter is confined to some areas, Devi is worshipped throughout the country. Matrilenial families are found in India only. This is an interesting theme for investigation by sociologists I feel that the Devi cult originated in the Dravidian tribes.