Why does the Turkish people think about unfair artificial boundaries been created between Greece and modern Republic of Turkey?

Not my business to answer for Turks, but

1. that map is wrong: Imbros/Gökçeada on the top right is Turkish.
2. The South China Sea islands are uninhabited; the Greek islands are full of ethnic Greeks. Just as with the Falklands, who lives there is slightly more important than geographical location.
3. We had a war, a mass population exchange, and a couple of treaties to deal with this. (And I get the impression that most of the ethnic Greek population of Imbros, who were meant to remain in place, have ended up in Australia.)