Shiva is beloved above all by Vishnu and Vishnu is the utmost favorite of lord Shiva because they are both one and the same having taken different forms to bless the devotees . The oneness and non duality of Shiva and Vishnu is explained , praised and proved in Vedas , Upanishads , puranas and epics.
In rudrahrudayopanishad
ये नमस्यन्ति गोविन्दं ते नमस्यन्ति शङ्करम्
येऽर्चयन्ति हरिं भक्त्या तेऽर्चयन्ति वृषध्वजम्
ये द्विषन्ति विरूपाक्षं ते द्विषन्ति जनार्दनम्
ये रुद्रं नाभिजानन्ति ते न जानन्ति केशवम्
yē namasyanti gōvindaṃ tē namasyanti ṡaṅkaram yē & rcayanti hariṃ bhaktyā tē & rcayanti vṛṣadhvajam yē dviṣanti virūpākṣaṃ tē
dviṣanti janārdanam yē rudraṃ nābhijānanti tē na jānanti kēṡavam
those who bows to govinda ( Vishnu ) bows to shankara ( shiva ) (i.e . ) both are pleased when we bow before any one of them .
Those who worship hari with devotion worship vrushadhvaja ( the one with the bull as his banner ) . One who hates viroopaaksha also hates janārdana . ( i.e . ) hating lord Shiva is equal to hating lord Vishnu . Lord Vishnu is also disrespected when lord Shiva is.
So no hater of Shiva can call himself a devotee of Vishnu and no hater of Vishnu can call himself a devotee of Shiva . Those who dont understand rudra don’t understand kevasha .
शिवाय विष्णु रूपाय शिव रूपाय विष्णवे
शिवस्य हृदयं विष्णुं:विष्णोश्च हृदयं शिवः
यथा शिवमयो विष्णुरेवं विष्णुमयः शिवः
यथाsन्तरम् न पश्यामि तथा मे स्वस्तिरायुषि
ṡivāya viṣṇu rūpāya ṡiva rūpāya viṣṇavē
ṡivasya hṛdayaṃ viṣṇuḥ viṣṇōṡca hṛdayaṃ ṡivaḥ yathā ṡivamayō viṣṇur - ēvaṃ viṣṇumayaḥ ṡivaḥ yathāntaram na paṡyāmi tathā mē svastirāyuṣi
Shiva is in the form of Vishnu and Vishnu is in the form of shiva . Vishnu is the heart of Shiva and Shiva is the heart of Vishnu . Vishnu is embodiment of Shiva and Shiva is embodiment of Vishnu . Till i understand this great secret I will be well and good .
The above mantra is found in the skandopanishad of yajurveda .
यथा शिवस्तथा विष्णुर्यथा विष्णुस्तथा शिव : ।
अन्तरं शिवविष्ण्वोश्च मनागपि न विद्यते । । - स्कान्द पुराने
yathā ṡivastathā viṣṇuryathā viṣṇustathā ṡiva : । antaraṃ ṡivaviṣṇvōṡca manāgapi na vidyatē । । - skānda purānē Vishnu is just as shiva and Just as Vishnu is shiva ; there is not even a minute difference between Vishnu and shiva .
Sivananda Lahari in Verse 82 says: Lord Vishnu, who took many forms, as Thy arrow, as Thy mount,
as Thy consort occupying half Thy body, as a boar, as Thy friend, as Thy drummer etc. and who offered his eyes at Thy feet(in place of a lotus flower) - that Vishnu, forming a part of Thy very being, is indeed the most worshipful among the worshipful? If not, he, who is there to excel him?
Mahavishnu is the greatest bhakta of Lord Parameshwara. he follows all methods of Bhakti and enjoys doing so, because he is always with his Lord in all these forms. he enjoyed serving the
Lord by taking many forms. When Lord Parameshwara went to destroy the three cities of the Asuras, Mahavishnu became the bow in His hand. The three cities represent the three states waking, dreaming and deep sleep. Mahavishnu being the protector of the people is used by Shiva as a bow for destroying the negative tendencies during those three states. Vishnu became the Mighty Bull Vrishabha and carried Lord Shiva wherever He wanted to go. Here Vishnu became the servant Dasyam of his Lord. Hari took the form of a boar to find out and reach the feet of the Lord, Here he is doing vandanam to the Lord. As Parvati the consort of Shiva, Vishnu became half
of the body of Shiva by surrendering everything Atmanivedanam. A seeker surrendering everything in him becomes one with Bhagawan, he becomes a part of Bhagawan. hari took the form of
Mohini to infatuate the Asuras while distributing the nectar got by churning the milky ocean. Later showed this form to his beloved Lord Parameshwara and became His friend(sakhya). When Lord Nataraja danced the Cosmic dance, Vishnu played the Mridangam.
The protection of the univer(continued)