Proof? As you say, we can’t look only at things like “most sold” or “number printed,” etc…
And the scriptures are read everyday by the Jewish people, and by Christians… The Catholics here can testify to that in the churches. And, we can all, Jews and Christians, can testify that many many believers read scripture every single day in synagogues and churches, as well as in our homes, at all times of the year. That doesn’t prove which book is true; Bible or Qur’an.
As this is an opinion question; there are books equal to the Qur’an, and books actually given by God which are holy scripture given by God Himself, first to the Jews, then to the Christians. I can’t speak for everyone else here, but for me, the Bible, as the word of God, is extraordinarily valuable to teach of God, to bring us closer to God, to help us praise God, worship God, love God, be amazed by God, to teach us His Law and what it means, how to live, how to die, and most important, to show us straight to Jesus Christ, who is the Son of God, Who in turn puts us in right relationship to God, and in that relationship to truly be able to call God; Father, and to read of His love. The Bible is the story of my family. No corruption, just truth.