Valmiki Ramayana Ayodhya Kanda  provides answer to this question. See [ Here][1]


  [1]: http://www.valmikiramayan.net/utf8/ayodhya/sarga1/ayodhya_1_frame.htm

> **तेषामपि महातेजा रामो रतिकरः पितुः |<br> स्वयम्भूरिव भूतानां बभूव गुणवत्तरः
> || २-१-६**
> 
>  RaamaH = Rama; svayambhuuriva = like the Brahma;bhuutaanaaM = among all the living beings; guNavattaraH = the most virtuous; teshhaamapi =
> among those brothers;mahaatejaH = the mightiest; ratikaraH babhuuva =
> was a source of joy; pituH = for his father.
> 
> **Rama, like the Brahma among all the living beings, the most virtuous**
> among those brothers and the mightiest was a great source of joy for
> his father.
> 
> 
> **स हि देवै रुदीर्णस्य रावणस्य वधार्थिभिः |<br> अर्थितो मानुषे लोके जज्ञे
> विष्णुः सनातनः || २-१-७**
> 
>  saH = That Rama; sanaatanaH = the eternal; vishhnuH= Vishnu; jajJNehi = was born; maanushhe loke = on the earth; arthita =
> as urged by; devaihi = gods; vadhaarthibhihi= to kill; udiirNasya
> raavaNasya = the egoistic Ravana.
> 
> That Rama - was He not the eternal **Vishnu** who was born on earth as
> prayed by celestials to kill the egoistic Ravana?


**Valmiki Ramayana Yuddha Kanda (Book of war) further declare that -**

 
> **प्रियते सततं राम: स हि विष्णु: सनातन:|<br>अदिदेवो महाबाहु हरी: नारायण: प्रभु: ।।**


Meaning -   Above all,  shree Ramachandra who is (part of) **Shree Vishnu** ,  which is sanatan. ie. Ever present. Shree Rama is **Adidev** ,   Mahabahu ,  **Hari** and literally **Shree Narayana** himself.