Well Rama's divinity is attested to by the gods themselves in the Yudhha Kanda Sarga 117. When Sita, whom Rama has told that she is free to go where she wants decides to enter the fire, all the gods appear there to tell Rama to stop her:
ततो हि दुर्मना रामः श्रुत्वैवम् वदतां गिरः |
दध्यौ मुहूर्तं धर्मात्मा बाष्पव्याकुललोचनः || ६-११७-१
Hearing the cries of these who were thus wailing, the virtuous minded Rama then became thoughtful for a while, afflicted as he was with melancholy, his eyes filled with tears.
ततो वैश्रवणो राजा यमश्च पृभिः सह |
सहस्राक्षश्च देवेशो वरुणश्च जलेश्वरः || ६-११७-२
षड्र्धनयनः श्रीमान् महादेवो वृषध्वजः |
कर्ता सर्वस्य लोकस्य ब्रह्मा ब्रह्मविदां वरः || ६-११७-३
एते सर्वे समागम्य विमानैः सूर्यसंनिभैः |
आगम्य नगरीं लङ्कामभिजग्मुश्च राघवम् || ६-११७-४
Thereupon, Kubera the King of Yakshas, Yama the lord of death together with the deceased ancestors, Indra the lord of celestials Varuna the lord of waters, the illustrious Shiva the great deity who bears the device of a bull as his banner and having three eyes, Brahma the creator of all the worlds and the best among the knowers of sacred knowledge all these together reaching the City of Lanka in aerial cars, shining like the sun approached Rama.
ततः सहस्ताभरणान् प्रगृह्य विपुलान् भुजान् |
अब्रुवंस्त्रिदशश्रेष्ठा राघवं प्राञ्जलिं स्थितम् || ६-११७-५ कर्ता सर्वस्य लोकस्य श्रेष्ठो ज्ञानवतां प्रभुः |
उपेक्षसे कथं सीतां पतन्तीं हव्यवाहने || ६-११७-६
कथं देवगणश्रेष्ठमात्मानं नावबुद्ध्यसे |
Lifting their long arms, their hands decked with ornaments, those excellent gods thereupon, spoke (as follows) to Rama who stood there, making a respectful salutation to them with his folded hands. "How do you, the maker of the entire cosmos, the foremost among those endowed with knowledge and an all-capable person, ignore Seetha who is falling into the fire? How do you not recognize yourself to be the foremost of the troop of gods?"
ऋतधामा वसुः पूर्वं वसूनां च प्रजापतिः || ६-११७-७
त्रयाणामपि लोकानामादिकर्ता स्वयं प्रभुः | रुद्राणामष्टमो रुद्रः साध्यानामपि पञ्चमः || ६-११७-८
अश्विनौ चापि कर्णौ ते सूर्याचन्द्रामसौ दृशौ | अन्ते चादौ च लोकानां दृश्यसे च परंतप || ६-११७-९
उपेक्षसे च वैदेहीं मानुषः प्राकृतो यथा |
"Among the Vasus, you are the Vasu named R^itadhama (one whose abode is Truth or the Divine Law) who was formerly the self-constituted ruler, the first creator of all the three worlds and the lord of creatures. You are the eighth Rudra among (eleven) Rudras and the fifth (Viryavan by name) among the Sadhyas. The twin Aswinis are your ears. The sun and the moon constitute your eyes. O the destroyer of the adversaries. You are seen (to exist) at the beginning and at the end of creation. Yet, you ignore Seeta, just like a common man."
भवान्नारायणो देवः श्रीमांश्चक्रायुधः प्रभुः || ६-११७-१३
एकशृङ्गो वराहस्त्वं भूतभव्यसपत्नजित् | अक्षरं ब्रह्म सत्यं च मध्ये चान्ते च राघव || ६-११७-१४
लोकानां त्वं परो धर्मो विष्वक्सेनश्चतुर्भजः | शार्ङ्गधन्वा हृषीकेशः पुरुषः पुरुषोत्तमः || ६-११७-१५
अजितः खड्गधृग्विष्णुः कृष्णश्चैव महाबलः |
"You are the Lord Narayana himself the glorious god, who wields the discus. You are the Divine Boar with a single tusk, the conqueror of your past and future enemies. You are Brahma, the imperishable, the Truth abiding in the middle as well as at the end of the universe. You are the supreme righteousness of people, whose powers go everywhere. You are the four-armed. You are the wielder of a bow called Sarnga, the lord of the senses, the supreme soul of the universe, the best of men, the invincible, the wielder of a sword named Nandaka, the all-pervader, the bestower of happiness to the earth and endowed with great might.
The Vaman Purana Section 1.8.5 mentions Lord Vishnu appearing as Vaman and Prahlad telling the same to his grandson Bali:
Lomaharshan says- "When Bali saw the demons becoming devoid of radiance and power, he enquired about the reasons from his grandfather, Prahlad. He wondered whether it was a bad omen. Prahlad went into a deep trance and saw the whole earth shaking violently. He also saw high tides rising in the ocean. He was convinced that these signs went to prove the inevitable emergence of the deities' power. Prahlad then meditated upon Lord Vishnu and found him manifesting in Aditi's womb as a Vaaman (dwarf). He also saw the whole universe existing in his body. Prahlad was surprised but the next moment he controlled himself and told Bali- "Now I know the reason why the demons have become devoid of their radiance and power. Lord Hari is about to take incarnation as the son of Aditi and this is the reason why all the demons have become powerless."
Bali curiously asked Prahlad- "Who is this Hari, the tormentor of the demons? Why should we be scared of him as we have many valiant demons who could defeat him easily." Prahlad became furious at Bali's utterances and cursed him by saying- "How dare you say like this! I am ashamed that you have taken birth as my grandson. I curse you to lose your kingdom and fall from grace because you have criticised Lord Vishnu- the supreme saviour."
The same is corroborated in the Shrimad Bhagvata Purana:
Mother of the gods, Aditi performed Payovrat as per the advice of her husband Kashyap. Pleased by her Vrat, the Lord appeared before her in Chaturbhuj (four-armed) form. Mother Aditi laid flat on the ground to greet the God. She prayed, "O Lord you are the God of Yagya, and Yagya yourself. Those, who take refuge at your feet are saved when you are pleased, nothing remains ungettable." Lord said, " O mother of the gods, I know about your desire. You have worshipped me for your sons, But it is difficult yet to defeat the demons. But because of your worship, I will protect your sons by becoming your child."
When the Lord arrived in Aditi's womb, Brahma prayed to Him. By Brahma's prayers, the unborn God appeared before Aditi. Shukdev says, "O Parikshit, on the twelfth day of the waxing phase of Bhadrapada month (corresponding to September) Lord took birth in Abhijit Muhurta. Everywhere, everybody celebrated the arrival of God with joy. The gods showered flowers on Him. The God had arrived in Vaman (dwarf) form. His continence appearance caused tremendous joy for the sages.
Vaman is further given gifts by all the other gods again showing his supremacy:
During Upnayan consecration of Lord, the ruling deity of the Gayatri mantra, Savitra preached Him the hymn. Guru gave him Yagyopavit, Kashyap gave neck-kerchief, the earth gave black buck skin, Chandra gave scepter, Mother gave loin cloth, the sky gave umbrella, Brahma gave Kamandalu, Saptrishi gave kush grass while Goddess Saraswati presented God with a string of Rosaries. Yakshraj Kuber gave him the alms bowl and mother Annapurnna gave him alms. Thus everyone payed due respect to God in Vaman incarnation who was radiating with divine glory.
Even the Rigveda mentions Vishnu in the form of Vaman as the Supreme Lord. Rig Veda Book 1 Hymn 154 states:
- I WILL declare the mighty deeds of Viṣṇu, of him who measured out the earthly regions, Who propped the highest place of congregation, thrice setting down his footstep, widely striding.
2 For this his mighty deed is Viṣṇu lauded, like some wild beast, dread, prowling, mountain-roaming; He within whose three wide-extended paces all living creatures have their habitation.
3 Let the hymn lift itself as strength to Viṣṇu, the Bull far-striding, dwelling on the mountains, Him who alone with triple step hath measured this common dwelling-place, long, far extended.
4 Him whose three places that are filled with sweetness, imperishable, joy as it may list them, Who verily alone upholds the threefold, the earth, the heaven, and all living creatures.
Again in Rig Veda Book 7 Verse 100
1 NE’ER doth the man repent, who, seeking profit, bringeth his gift to the far-striding Viṣṇu. He who adoreth him with all his spirit winneth himself so great a benefactor.
2 Thou, Viṣṇu, constant in thy courses, gavest good-will to all men, and a hymn that lasteth, That thou mightst move us to abundant comfort of very splendid wealth with store of horses.
3 Three times strode forth this God in all his grandeur over this earth bright with a hundred splendours. Foremost be Viṣṇu, stronger than the strongest: for glorious is his name who lives for ever.
In fact most other Avatars are mentioned in similar glowing terms. In Chapter 18, Canto 5 of Shrimad Bhagavatam we find the following passages:
(8) 'Oh Supreme Lord NARASIMHA, I bow for You, my obeisances to the power of all power that You are. Please manifest Yourself fully, oh You whose nails and teeth are like thunderbolts. Please take away the desire to enjoy the untrue, be so good to drive away, oh Lord, the ignorance in the material world. May, with my oblations, there be freedom from all fear, I beg You, oh Lord, source of my prayer, to appear before my mind's eye.
(30) 'My Lord, our respects for You, the Supreme Lord in the form of a KURMA. You are the embodiment of all good qualities, again and again we offer You our obeisances whose position cannot be discerned, You the greatest one, He who reaches everywhere and the Shelter of All. (31) This form of You of the visible cosmic complete which You manifested by Your creative potency and is known by so many appearances, is beyond any measure and we therefore cannot perceive it as it is - unto You, whose actual form cannot be expressed in words, our respects.
(34) Also in the northern territory called Kuru there is the Supreme Lord, the Original Person of Sacrifice, in His boar form VARAHA. There He is over and over worshiped by the Goddess and this planet earth, together with the inhabitants of [Uttara-]Kuru who are unrelenting in their devotional service unto Him. In this worship the following Upanishad verses are repeated: (35) 'We offer the Supreme Lord our obeisances who is understood by means of the different mantras for the sacrifices, the rituals and all the great ceremonies that are part of His body. That great personality, the purifier of our karma who manifested Himself in all the three [previous] ages we offer our respects.
Similar prayers are dedicated to Lord Rama, Pradyumna, Nar-Narayan and others.