Imam Sadiq(as) said: Eid-e-Ghadeer is the greatest Eid of Allah(swt)
(Ref: Wasail ush shia, Vol 5, Pg 224)

The closed schools and workplaces, clean and shining roads, perfumed houses, happy smiling people with rose like faces, new dresses, variety of meals and the noise of playing kids, which day does you remember by all this??? Everyone will say that all these things are the signs of “Eid-day”. This is the atmosphere on “Eid-ul-Fitr” or Eid-ul-Azha”. The only difference between the two is that, “Fitra” is paid on one of the days and “Sacrifice” is offered on another.
Pleasure and happiness of these days are very important to everyone hence along with elders, the youths and children impatiently wait for the Eid-Day. Hence every year “Eid” is celebrated with great enthusiasm. People want to share the happiness, hence even if they don’t usually help the needy, on “Eid-Day” they make it a point to help. Besides this, if there happens to be death of someone’s family member before Eid and there is atmosphere of sorrow in that house, then in India and Pakistan usually the vermicelli is send and in other countries sweets are send to them.
You must be thinking that what’s the point in reminding all these things??? Well! There is definitely an aim behind it, which is to ask an important question.
The question is, whether these two are the only “Eids” for the celebrations and happiness????? There are two answers to this question.
First Yes! As there is no Eid for Muslims other than “Fitr” and Azha” (Friday is considered to be a weekly Eid with limited joy).
Second No! But the problem is that our way of Eid celebrations reveals something else, due to being influenced by common Muslims.
Those who believe in the Wilayat of Ahlulbait (as) do admit at heart and say that the Greatest Eid” is “Eid-ul-Ghadeer”.
But this belief has to be put in action, because there are a lot of Ahadith from Infallibles (as) on this matter
The readers may decide themselves that our routine works and business on “Eid-ul-Ghadeer” speak volumes! (Although we do enjoy a separate “Eid-Holiday” even if the holiday was announced some other day due to moon sighting problems).
What is proved by no special arrangements in our houses, dresses, meals etc???
Do we consider “Eid-ul-Ghadeer” to be greater than “Fitr” and “Azha”???
Well! Congratulations to those who celebrate in a special way (Juloos and Jashn of Ghadeer). But generally we see that the celebration in Ghadeer is not even equal to “Eid-ul-Fitr” and “Azha”. We would like to draw your attention towards a very important point in the end. All the other Eids are called “Eid-al-Lil-Muslimeen” i.e. Eid for the Muslims, but “Eid-ul-Ghadeer” is called to be the great Eid of the great Lord. Hence we pray that all the followers of Wilayat may celebrate “Eid-ul-Akbar” (great Eid) in the great manner and get the Tawfiq of propagating Wilayat as a gift on Eid-Day.
Metioned below are some ahadees highlighting the importance of Eid-e-Ghadeer
(1) Imam Jafar Sadiq (as) said: “Fasting on the day of Ghadeer is equivalent to fasting throughout the entire age of the world… It is the greatest festival of Allah. Allah has not sent any prophet but that he celebrated this day as Eid and was aware of its sanctity. It is known in the heavens as ‘The Day of the Famous Covenant’… You might think that Allah, the mighty and the majestic, has created a day more sacred than that. No, by Allah! No, by Allah! No, by Allah!"
(Complete hadees is not quoted here)

[Source: Tahdhib Al Ahkam – Sheikh Toosi Vol.3 Pg.143]

(2) Imam Raza (as) narrates from his father (as): “Certainly, the day of Ghadir is more famous in the heavens than in the earth… and by Allah, had people truly known the superiority of this day, the angels would have been shaking hands with them ten times a day.”
(Complete hadees is not quoted here)
[Source: Tahdhib Al Ahkam – Sheikh Toosi Vol.6 Pg.24]
Some points on the sermon of ghadeer delivered by the Holy Prophet(saww) which you might not have read or heard are mentioned below:
(1) The Prophet (PBUH&HF) explicitly mentioned the name of Imam Ali (PBUH) in his sermon about forty times besides many more instances that he (PBUH&HF) referred to him by pronoun.

(2) He (PBUH&HF) repeatedly used the following titles for Imam Ali (PBUH) in this sermon:
- Wali and Mawla (guardian) fifteen times.
- Imam (leader) twelve times.
- Amir (commander) seven times.
- Wasi (executor of the will and deputy of the affairs) seven times.
- Akh (brother) four times.
- Khalifa (successor) three times.
- Hadi (guide) three times.

(3) The Prophet explicitly mentioned the word
A’imma (Imams), referring to the eleven Imams after Imam Ali (PBUH), nine times in his sermon.
(4) The sermon also refers to over one hundred verses of the Holy Quran concerning Imam Ali
(PBUH) and his authority, his followers, and their enemies.
(5) The number of sentences categorized by some important subjects of the sermon is as follows:
- Over fifty sentences on the
Walaya of Imam Ali (PBUH).
- Twenty sentences about his virtues, yet stressing that it is impossible to enumerate all his virtues in the sermon.
- Twenty-five sentences about the followers (Shia) of Imam Ali (PBUH) and their enemies.
- Ten sentences on the Walaya of the Imams (PBUT) after him.
- Twenty sentences specifically about Imam Mahdi (PBUH), the last divinely appointed Imam who will establish the divine government on earth at the end of time.
- Twelve sentences about the importance of the Quran, and introducing Imam Ali (PBUH) and his children as its exclusive authorized interpreters.
- Ten sentences on urging people to pledge their fealty to Imam Ali (PBUH) and the Imams after him from his offspring.