Turkey is too big, too Islamist and too un-European for the EU; it is too little Islamist and a disliked former colonial power for most of the Arab street; a sectarian and regional rival for Iran, and a security threat to the bigwigs in the Shanghai Cooperation Organization.
Theoretically, Turkey is a NATO ally. In reality, it is a part-time NATO ally. It became the first member state that had military exercises with the Syrian army and the Chinese Air Force; awarded a NATO-sensitive air defense contract to a Chinese company; supported jihadists in Syria and the Muslim Brotherhood elsewhere in the Middle East; allied with what NATO nations view as a terrorist organization (Hamas); shared, until recently, an embarrassing list of potentially terrorist-sponsoring countries with seven others including Syria and Pakistan, and sported a population with the lowest support for the NATO alliance.
Also, theoretically, Turkey is a member candidate of the European Union [EU]. In reality, since 1974, Turkey has been occupying one-third of the territory of an EU member state, Cyprus; it boasts a record number of violations of human rights, according to rulings by the European Court of Human Rights; it remains the EU's dreaded problem in most areas of fundamental policy; it habitually (and undiplomatically) ignores EU calls for broader freedoms; and it is gripped by a deep distrust of the EU. A most recent survey, "Public Opinion in The European Union – November 2014," conducted by the European Commission's Eurobarometer, revealed that only 18% of Turks trust the EU.
Just recently, Russia's prime minister, Dmitry Medvedev, recalled a joke by his predecessor Viktor Chernomyrdin [prime minister between 1992 and 1998] who once was asked by a journalist when Ukraine could join the EU. "After Turkey," Chernomyrdin replied. When should we expect Turkey to become a member, asked the journalist. "Never," he said.