This may well be regarded as quite a contentious issue by some supporters of the restitution of the Elgin Marbles, but does Turkey have as much right to request the return of cultural treasures that they have lost?
Key differences between the cases are that generally speaking, while artefacts have been taken from Turkey & placed in foreign museums, these artefacts were not created by the Turks initially their current sense of responsibility for the artefacts remaining in their country is to be commended though.
The other difference is the circumstances under which the items were removed from Turkey, where they were taken from Turkey under the control of the Turks, rather than from a country that was under foreign occupation.

From:
[1] Turkish Daily News

People want stolen treasures returned:
Gila Benmayor
Saturday, February 26, 2005

I assume everybody knows that Turkey is full of historic and cultural treasures.

Unfortunately, much of it has been stolen and taken overseas.

Just think about the Bergama Museum in Berlin and the Treasure of Troy at the Pushkin Museum in Moscow.

Whenever I go and visit the Bergama Museum, I am always amazed how an entire temple was moved there.

It’s not only the temple. There are also the mosaics stolen from Antakya at the Louvre Museum. No matter what important museum you visit around the world, you will definitely see a piece stolen from Turkey.

Now, the people of Bodrum are preparing to go to the European Court of Human Rights for the return of artifacts stolen from Halicarnassos.

They announced their intention at the EMITT Tourism Exhibition in Istanbul. Bodrum Mayor Mazlum Ağan, the director of the documentary Antique Halicarnassos Remzi Kazmaz, nongovernmental organizations, artists and lawyers are ready to apply to the court to demand the artifacts back. I believe the Halicarnassos Mausoleum is at the British Museum in London.

Melina Mercouri, who was the Greek culture minister, had tried very hard for the return of the Elgin Marbles from the British museum. Her dream was to see the day of their return. She was not successful.

I hope the people of Bodrum are luckier.