This Blessed Name (Allaah Ta’ala) is more exalted from amongst the Ninety-Nine Beautiful Names according to most ulamaa (scholars), since it encompasses all His Qualities.
Sheikh Abdul Qaadir Jilaani Rahmatullaahi Alayh said:

“The isme-a’zam is the word ‘Allaah’(Ta’ala) on condition that you say ‘Allaah’ (Ta’ala) and there is nothing else in your heart.” (Mirqaat)

This means the heart must only be turned to Allaah Ta’ala.
The speciality of this Great Name which the ulamaa (scholars) have stated, is that this Name Encompasses all qualities, whether of Glory or Beneficence.
This Sublime Name is used exclusively for the Exalted Creator ,and Sustainer . Its designation is only for that Being Who is One and has no partner. Just as there are no partners or equals in His Being ,and Attributes , similarly there are no partners in this Exalted Name.
For this reason, the teachings of all the Friends of Allaah Ta’ala is that the Name of His Being (Allaah Ta’ala) is the isme-a’zam (the Supreme Name). Imaam-A’zam Abu Haneefaa RadhiAllaahu Anhu also has stated that the name ‘Allaah’ is the isme-a’zam as Imaam Tahaawi Rahmatullaahi Alayh has narrated.

The proof is:
1) The name ‘Allaah’ denotes all the Beautiful Names and Lofty Qualities.
2) This Name (‘Allaah’) cannot be used for any other being besides His Being. Allaah Ta’ala has stated: “Do you know any such being who has the same Name (qualities) of Allaah?”
(Maryam verse 65) This is not so, thus the Name ‘Allaah’ is only used for the Being of Allaah Ta’ala.
3) All the Beautiful Names are attributed to the word ‘Allaah’. The rule is that towards whichever word something is attributed, that word is definitely superior. From this rule, we learn that the actual described word (mausoof) is ‘Allaah’.
Thus ‘Allaah’ is the Most Superior of all the Beautiful Names. Besides this, a person can say that Rahmaan, Raheem, Malik, Quddoos are all Names of Allaah Ta’ala.
However, it cannot be said that ‘Allaah’ is a Name of Rahmaan or Raheem. Thus, it is established that the Original Name of all names is ‘Allaah’.

Note:
A.) The Name of Allaah Ta’ala should be taken with respect. Whenever the Name of Allaah Ta’ala is taken, whether in speech or writing, then one should also add Subhaanahu Ta'ala or Jalla Jalaalahu. Hadhrat Bishr Haafi Rahmatullaahi Alayh was asked the reason for his widespread acceptance, as his name had become famous amongst the people just like the names of the Messengers Alayhis Salaam.
He answered, “It is only due to the Grace of Allaah Ta’ala. It is not due to any excellence within me. I was an open sinner and a person who loved to fulfil my desires. It so happened that I once saw a piece of paper on the road. I lifted it up and saw that "Bismillahir Rahmaanir Raheem" was written on it. I cleaned it and placed it in my pocket.
I only possessed two dirhams at that moment. I went to a perfume shop, and I bought a certain type of perfume (ghaaliya) with the two dirhams. (Ghaaliya is a perfume prepared from musk, amber, aloe wood (Oud) and scented oil). I applied perfume to this piece of paper.
That night when I slept, I heard someone saying,
‘O Bishr, you raised Our Name from the path and fragranced it, I will fragrance your name in this world and the hereafter.’”
(Kitaabut-Tawwaabeen of Maqdasi)

B.) The Name of Allaah Ta’ala should be taken in abundance. Hadhrat Maulana Ashraf Ali Thaanwi Rahmatullaahi Alayh in one of his lectures said: “Allaah Ta’ala has such a great status that if one had to address Him with such forms of addresses which are appropriate for His position, as is done for the kings of the world, then a person’s whole life would pass, and he would not get the opportunity to take the name of Allaah Ta’ala even once.
The titles and forms of address would never terminate. People would fear to take His Name, however, Allaah u Akbar ! (Allaah Ta’ala is the Greatest!), how Merciful is He, that He has not placed any restrictions in taking His Name.

At any time and in any condition, when one desires, one can take His Name and address Him, save for a few particular places and conditions, when making dhikr with the tongue is contrary to etiquette. Thus, whether poor or rich, worshipper or sinner, everyone has permission to take His Name without any formalities. Otherwise, the demand of His Grandeur and Magnificence is such, that if our tongues were cleansed with the water of the seven oceans, it would still not be suitable to take His Name.
Look at His Mercy! How easy has He not made it for His Slaves to utter His Name?” (Husnul-Azeez)

C.) An endeavour should be made to gain the Love of Allaah Ta’ala. Rasulullaah SallAllaahu Alayhi Wasallam used to supplicate :
“O Allaah! I request from You the pleasure of gazing at your Being, and the yearning to meet You .” (Nasai)

This desire was always in the heart of Sayyiduna Rasulullah SallAllaahu Alayhi Wasallam to meet his Rabb (Sustainer).The lover’s heart is always drowned in the beauty and the sight of his beloved. When he glances towards his beloved’s grandeur, then he realizes his greatness, and awe is created in his heart for him. When he looks towards his beloved’s beauty, then love for him is created and an intense desire to meet him is born.

Hadhrat Yahyaa ibn Muaaz RadhiAllaahu Anhu said, “When an aarif (one who has recognised Allaah Ta’ala) leaves this world, his desire for two things are not fulfilled
1) crying over himself
2) having desire to meet his Rabb.”

Hadhrat Abu Ubaidah Al-Khawaas RadhiAllaahu Anhu was walking on the road when suddenly he exclaimed, “O how much yearning I have to meet that Being who sees me whereas I cannot see Him!”