The people in Islamic countries were pagans that worshipped idols. All nations had their own idols and gods.

I don't know about the other nations but the Turks accepted (and were forced into) Islam mostly when they were settled in Central Asia. During those times, a sizeable number of Turks were following shamanistic and animistic beliefs. Besides, those who were in frequent contact with China were supporting Confucian ideas. However, historians with relevant knowledge on ancient Turkish religions propose that as a nation Turks were generally united under a religion of the "Sky God". The religion of the "Sky God" used to support the already militaristic and rigid social life of the Turks. Although it was a religion which resembled monotheism, belief of the "Sky God" incorporated many shamanistic and animistic ideas in itself. It was a common practice in ancient Turks to revere natural elements such as fire, water, etc. in addition to their belief that trees, rivers and animals were holy. (It is important to note that the formal history education in Turkey strongly asserts that this religion of the "Sky God" was extremely similar to Islam in practices and beliefs, to such an extent that one would assume Turks had always been an Islamic nation! Of course, this has never been so).

"What religion did people in Islamic countries practice before Islam came into being?" ... "Cultural diffusions impacted Arabia as elsewhere in the world. In Arabia were the descendants of Jewish refugees from centuries before. By 500 CE Christian missionaries had arrived in Arabia. Before the rise of Islam, the entire Arabian province of Najran had been Christian. Christianity was established superficially in various other centers of trade, and Arabs living on the borders of what was left of the Roman and Persian empires had contacts with people and ideas from those empires." (www.fsmitha.com) ... just passing the info along! Thank you.

although there were large populations of Christians and Jewish Arabs in the area, the people of Mecca were pagans. The Quran says so. The Ka'aba was already there, but full of statues of pagan deities, including the Moon God, Al-Ilah ("The god") and his daughters, Al-Lat, Al- Uzza and Al-Manat. These three are mentioned in the Quran in Sura 53:20. Although Muhammed cleared out many of the idols from the Ka'aba, Al-ilah and his daughters remained dear to the hearts of the Meccans. Early versions of the Quran have the verses: Have you thought of al-Lat and al-'Uzza and Manat the third, the other. These are the exalted Gharaniq, whose intercession is approved. They were later said to have been written under the influence of Satan, and so are called "the Satanic Verses".

Sufism was practiced before Islam. Also Zorastrianism was practiced from 1200BC.