Brahma, Vishnu and Shiva are considered to be the "Hindu trinity". But who is the supreme. Srila Prabhupada explains this point in the following purport.
The transcendental personality of Godhead is indirectly associated with the three modes of material nature namely goodness, passion ignorance and just for material world's creation, maintenance and destruction He accepts the three qualitative forms of Brahma, Vishnu and Maheswara trio. Out of them the Form of the quality of Goodness (Vishnu) is just suitable for deriving the ultimate benefit for all human beings.
PURPORT
Why Lord Shri Krishna by His plenary parts shall be rendered devotional service as it is explained above, is confirmed by this statement. Lord Shri Krishna and all His plenary parts are Vishnu Tatwa or the Lordship of Godhead. From Sri Krishna the next manifestation is Valadeva. From Valadeva is Samkarshan, from Samkarshan is Narayana again from Narayana there is the second Samkarshan and from this Samkarshan the Vishnu Purusha Avatars. The Vishnu or the deity of the quality of goodnes in the material world is the Pursha Avatara known as Khirodashayee Vishnu or Paramatama. Brahma is the deity of Rajas (passion) and Shiva for ignorance. They are three departmental heads of the three qualities of this material world. Creation is made possible by the quality of passion and endeavour, it is maintained by the goodness of Vishnu and when it is required to be destroyed Lord Shiva does it by Tandab Nritya. The materialists and the foolish human beings do worship Brahma and Shiva respectively. But the pure transcendentalists do worship the Form of Goodness Vishnu in His various Forms. Vishnu is manifested by His millions and billions of integrated forms and separated forms. The integrated forms are called Godhead and the separated forms are called the living entities or the Jivas. But either the jivas or Godhead both of them have their original spiritual forms. The Jivas are sometimes subjected under the control of the material energy but the Vishnu forms are always controller of the material energy. When Vishnu or the Personality of Godhead appears in the material world He comes to deliver the conditioned living beings who are under the material energy. Such living being appears in the material world with intention of lording it over falsely and thus become entrapped by the three modes of nature. As such the living entities have to change the material coverings for undergoing different terms of imprisonment. The prison house of the material world is created by Brahma under instruction of the Personality of Godhead and at the conclusion of a Kalpa the whole thing is destroyed by Shiva. But so far maintenance of the prison house is concerned it is done by Vishnu as much as the state prison-house is maintained by the state. Any one, therefore, who may wish to get out of this prison house of material existence which is full of miseries like repetition of birth, death, diseases and old age, he must please Lord Vishnu for such liberation. Lord Vishnu is worshipped by devotional service only and if any one has to continue the prison-life in the material world he may ask for relative facilities from the different demigods like Shiva, Brahma, Indra, Varuna, etc. for temporary relief. No such demigods can however release the imprisoned living being from the conditioned life of material existence except Vishnu. As such the ultimate benefit may be derived from Vishnu the Personality of Godhead.
Srimad Bhagavatam 1.2.23 sloka and purport