Hinduism is the oldest of all the religions and thus the, most pure, authentic and best of all the religions of the world.

1.  Islam is the oldest religion
Hinduism is not the oldest of all the religions. It is Islam which is the first and the oldest of all religions. People have a misconception that Islam is 1400 years old and that Prophet Muhammad (pbuh) is the founder of this religion. Islam existed since time immemorial, ever since man first set foot on this earth. Prophet Muhammad (pbuh) was not the founder of Islam. He was the last and final Messenger of Almighty God.

2.  The oldest religion need not be the purest and the most authentic religion
A religion cannot be claimed to be most pure and authentic, only on the criterion that it is the oldest. It is similar to a person saying that the water he has kept in an open glass, in his house, outside the refrigerator, for three months is purer than the water which has just been collected in a clean glass, immediately after it has been purified.

3.  The latest religion need not be the purest and the most authentic religion
On the other hand a religion cannot be claimed to be the purest or authentic, only on the criterion that the religion is new or the latest. A bottle of distilled water which is sealed, packed and kept in the refrigerator for three months is much purer than a bottle of water freshly collected from the sea.

4.  For religion to be pure and authentic, it should not have interpolations, changes and revisions in its scriptures revealed from God
For any religion to be pure and authentic, its scriptures should not contain any interpolation, addition, deletion or revision. Moreover the religion’s source of inspiration and direction should be Almighty God. The Qur’an is the only religious scripture on the face of the earth which has been maintained it its original form. All the other religious scriptures, of all the other religions have interpolations, additions, deletions or revisions. The Qur’an has been in the memory of a multitude of people, intact in its original form ever since its revelation, and now there are hundreds of thousands of people who have preserved it in their memory. Moreover, if you compare the copies made by Caliph Uthman from the original Qur’an which is yet present in the museum in Tashkent and in Koptaki museum in Turkey, they are the same as the ones we possess today.

Allah (swt) promises in the Qur’an, in Surah Al Hijr, chapter 15 verse 9

"We have, without doubt, sent down the Message; and We will assuredly guard it (from corruption)."

5.  The oldest religion need not be best religion
A religion cannot be claimed to be the best religion only on the criterion that it is the oldest. It is similar to a person saying, that my 19th century car is better than a Toyota car manufactured in 1998, because it is older. He would be considered to be a fool to say that his 19th century car which required a rod to be turned in circles to start it, is better than a key-start 1998 Toyota car, just because it is older.

6.  The latest religion need not be the best religion
On the other hand a religion cannot be called as the best religion only on the criterion that the religion is new or that it came later. It is similar to a person who says that my 800 cc Suzuki car manufactured in 1999 is better than a 5000 cc Mercedes 500 SEL manufactured in 1997. To judge which car is better, a person should compare the specifications of the car e.g. the power of the car, safety measures, the capacity of the cylinders, the pickup, the speed, the comfort, etc. 5000 cc Mercedes, 500 SEL car manufactured in 1997, is far superior and better than a 800 cc Suzuki (Maruti Suzuki 800) manufactured in 1999.

7.  A religion is best, if it has the solutions to the problems of mankind
For a religion to be considered the best, it should have the solution to all the problems of mankind. It should be the religion of truth, and should be applicable to all ages. Islam is the only religion which has the solution to all the problems of mankind. e.g. the problem of alcoholism, surplus women, rape and molestation, robbery, racism, casteism, etc.

Islam is the religion of truth, and its laws and solutions are applicable to all the ages. The Qur’an is the only religious book on the face of the earth, which has maintained its purity and authenticity proving itself to be the word of God in all the ages. i.e. previously, when it was the age of miracles, literature and poetry and in present times when it is the age of science and technology. Moreover, Islam is not a man-made religion, but a religion revealed and inspired by Almighty God. It is the only religion acceptable in His Sight.