Who else than Nārāyaṇa could be the greatest devotee of Parameśvara?
Śrī Appayya Dīkṣitendra has beautifully answered this in his Śikharinīmālā, based on scriptures:
VERSE 11:
अपारं विज्ञातुं गिरिश, महिमानं तव परं विधातुं भक्ति वा तव चरणयोनित्यमचलाम् । प्रसादं वा लब्धुं वरद, तव पूजाभिरधिकं जगत्येकः शक्तो जयति वनमाली स भगवान् ॥११॥
"O Śiva, only god Nārāyaṇa alone in the world is able to know your great immeasurable glory. He alone is able to constantly practice steady devotion at your feet. He alone is able to gain your excessive grace with worships, O giver of boons! The god Nārāyaṇa is ever victorious."
PROSE DISCLOSURE:
By mentioning the grace, it follows that the attainment of all desired goals is fulfilled. Therefore, it is not separately mentioned.
Viṣṇu's knowledge of the glory of Śiva and his great devotion to Him are proved in the Kūrma Purāṇa statement: "कृष्णद्वैपायनः साक्षाद्विष्णुरेव सनातनः । को ह्यन्यस्तत्त्वतो रुद्रं वेत्ति तं परमेश्वरम् ॥ १,२८.६५ ॥ ... नार्जुनेन समः शंभोर्भक्त्या भूतो भविष्यति । मुक्त्वा सत्यवतीसूनुं कृष्णं वा देवकीसुतम् ॥ १,२८.६३ ॥ - Kṛṣṇa Dvaipāyana is none other than the eternal Viṣṇu Himself. Who else indeed, apart from him, can truly know Rudra, the Supreme Lord? In devotion to Śambhu, none shall ever equal Arjuna—save only the son of Satyavatī (Vyāsa), or Kṛṣṇa, the son of Devakī".
Now there is a statement in the fourth skandha (4.6.7) of the Bhāgavata Purāṇa in which Brahmā addresses gods who are praying to pacify Śiva who was angered during the sacrifice of Dakṣa, "नाहं न यज्ञो न च यूयमन्ये । न देहभाजो मुनयश्च तत्त्वम् । विदुः प्रमाणं बलवीर्ययोर्वा । तस्यात्मतन्त्रस्य कउपायं विधित्सेत् ॥ ७ ॥ - Neither I (Brahmā) nor Yajña, nor you nor sages or any embodied being, knows his real nature and the extent of his strength and power. Who indeed could devise any means to govern Him, who is entirely self-dependent?".
There is also a statement in the eighth skandha (8.7.32) of the same work in which the gods address Śiva "न ते गिरित्राखिललोकपाल विरिञ्चवैकुण्ठसुरेन्द्रगम्यम् । ज्योतिः परं यत्र रजस्तमश्च सत्त्वं न यद्ब्रह्म निरस्तभेदम् ॥ ३२ ॥ - Oh Lord of mountains! Your supreme effulgence where the modes of Prakṛti like sattva, rajas and tamas have no place, and which is nothing but the supreme Brahman transcending all distinctions and differentiations, is absolutely inaccessible to all the guardian deities of various spheres and to Brahmā, Vaikuṇṭha and Indra".
Such statements emphasize the difficulty for others to comprehend the reality of Śiva. They do not mean that Hari is ignorant of Him; therefore, there is no contradiction. Indeed, Viṣṇu is intent upon worshipping Śiva above all, and Śiva bestows most favours upon Him.
Thus it is said in a statement by Śiva in sauptikaparva (10.7.61) "यथावदहमाराद्धः कृष्णेनाक्लिष्टकर्मणा । तस्मादिष्टतमः कृष्णादन्यो मम न विद्यते ॥६१॥ - I am duly worshipped; by Kṛṣṇa who is unwearied in action; therefore none else exists who is dearer to me than Kṛṣṇa".
Vyāsa also points out in the Droṇa Parva of the Mahābhārata (7.202,92-96 in Summary) "देवदेवस्त्वचिन्त्यात्मा अजय्यो विष्णुरव्ययः । सर्वरूपं भवं ज्ञात्वा लिङ्गेऽर्चयति तं विभुम् ॥ तस्मिन्नभ्यधिकां प्रीतिं करोति वृषभध्वजः । - Viṣṇu, the unconquerable, imperishable Lord of gods, knowing Bhava as the All-formed, worships Him in the liṅga; unto him, the Bull-bannered Lord shows greater love than to any other".
He gains the highest seat because of the grace of Śiva. It is shown in the Mantravarṇa (Ṛgveda 5.3.3) which introduces Liṅga as the place of manifestation of Śiva in "तव श्रिये मरुतो मर्जयन्त रुद्र यत्ते जनिम चारुचित्रम् - For your glory (तव श्रिये), the Maruts cleanse you (मरुतो मर्जयन्त), upon your birth (रुद्र यत्ते जनिम) which is wonderful and awe-inspiring (चारुचित्रम्)." and specifies it by "पदं यद्विष्णोरुपमं निधायि तेन - The abode, which is similar to Viṣṇu, was established down by this". Its meaning is explained in the Parāśara Purāṇa: "रौद्रं लिङ्गं महाविष्णुर्भक्त्या शुद्धं शिलामयम् ॥१५॥ चारुचित्रं समभ्यर्च्य लब्धवान् परमं पदम् । या च लक्ष्मीः समाख्याता महाविष्णोश्च वल्लभा ॥१६॥ - The Raudra Liṅga, which is pure and made of stone, wonderful and oddly shaped was worshipped with devotion by Great Viṣṇu whereby which He gained the supreme abode as well as, Lakṣmī to enumerate, who is dear to Mahāviṣṇu". In the caturbhujābhiṣeka chapter of the Kāśīkhaṇḍa, it is described that Śiva coronated Viṣṇu and gave him many boons such as the abode of Vaikuṇṭha, Lordship over the whole world, valour more than Himself which are not easy to obtain by others.
In the description of the tīrthayātrāvidhi in the Vana Parva of the Mahābhārata (3.84,16-18), it is said that "ततो गच्छेत्सुवर्णाक्षं त्रिषु लोकेषु विश्रुतम् । यत्र विष्णुः प्रसादार्थं रुद्रमाराधयत्पुरा ॥१६॥ वरांश्च सुबहूँल्लेभे दैवतेषु सुदुर्लभान् । उक्तश्च त्रिपुरघ्नेन परितुष्टेन भारत ॥१७॥ अपि चास्मत्प्रियतरो लोके कृष्ण भविष्यसि । त्वन्मुखं च जगत्कृत्स्नं भविष्यति न संशयः ॥१८॥ - Then [the pilgrim] should proceed to Suvarnākṣa, the [sacred site] famed throughout the three worlds where of old Viṣṇu propitiated Rudra to win his favour and received from him many boons hard to win even for the gods. And Tripurāgni, being pleased [with his devotion], declared: "O Kṛṣṇa, you will be the man most dear to me in the world; and the whole world will turn to face you [in adoration]. Of this there is no doubt".
In the chapter on austerities in the Droṇa Parva, it is mentioned that Śiva gave the Supreme Valour to Nārāyaṇa who pleased Him by practising penance for sixty thousand years in the Mainaka Mountain. And in the Pārijāta Saṃhitā of the Harivamśa it is said "इति संस्तूयमानस्तु भगवान् गोवृषध्वजः ॥ १३३३ ॥ प्रसार्य दक्षिणं हस्तं नारायणमथाब्रवीत् ॥ १३३४ ॥ मनीषितानामर्थानां प्राप्तिस्तेऽस्तु सुरोत्तम ॥ १३३५ ॥ पारिजातं च हर्तासि मा भूत्ते मनसा व्यथा ॥ १३३६ ॥ यथा मैनाकमाश्रित्य तपस्त्वमकरोः प्रभो ॥ १३३७ ॥ तथा मम वरं कृष्ण संस्मृत्य स्थैर्यमाप्नुहि ॥ १३३८ ॥ नीत्वोदकेन दिव्येन स्नापयिष्यसि केशव ॥ १३३८ ॥ अवध्यस्त्वमजेयश्च मत्तः शूरतरस्तथा ॥ १३३९ ॥ भवितासीत्यवोचं यत्तत्तथा न तदन्यथा ॥ १३४० ॥ - Thus eulogised the god Mahādeva, having the bull for his emblem, extended his right arm on the head of Nārāyaṇa and thus spoke (35):—"O best of gods, thou shalt obtain the things desired by thee; thou shalt carry away the Pārijāta tree; and thy mind shall not feel the least pain (of disappointment) (36). O powerful Kṛṣṇa, do thou compose thyself remembering the austerities thou didst practise on the Maināka mountain and the boon I bestowed on thee on that occasion (37). ‘Thou shalt be incapable of being slain’, ‘Thou shalt be invincible,’ and ‘Thou shalt be ever more indomitable than myself’—these and such words which I spoke to thee then-shall be so and not otherwise (i.e. they shall be true to the letter) (38)".
Thus, all that [which] is set forth in the Śaiva, Linga, and related scriptures must be viewed in this light.
Namaḥ Śivāya 🔱