thanks for advice. I have time to think and of course I can't be sure if I go anywhere because the decision doesn't depend on me...

heyy my friend please choose cukurova university...i guarantee you will like it...it has a marvellous picturesque campus....and it has good atmosphere to study and i want to add that not to cheat you...its not so much famous as middle east university.....i think you should check the pictures of cukurova before make a decision.....

http://www.cukurova.edu.tr/Content/Asp/Turkish/UnivAlbum.asp

İstanbul universty is the biggest and the oldest universty in Turkey. METU is a good universty too. but if u ask me, if u are foreigner in turkey u must choose a big city like istanbul and ankara.

The instruction language is English at Metu while in İstanbul Unv. and Çukurova Unv. it isn't.
Metu has lots of foreign students and the number of foreign students is probaby a few times more than the total of Istanbul and Çukurova Unv. have. At metu there will be more tolerance to different lifestyles and untraditional ways of living. Inside the campus there is much more independence and flexibility and noone really cares for others so much. What I mean by flexibility is something you will only understand if you actually require the flexibility and freedom in your life.
Metu also can provide a good accommodation as it has many facilities.
I studied a few years at Metu and I can tell you that if you go to Metu you will never want to go to somewhere else. The other universities you mentioned are not bad but there is a clear difference in many ways.