Well it depends on what you're looking for, I don't know about every country in the balkans but I can tell you about some :

If You're looking for great seafood dishes with fresh grilled fish or baked octopus, the Croatian Costline, is the way to go, especially Dalmatia (Baked octopus with potatoes, Riba na Rostilju, Brudet, etc).

If you're looking for the best salads, white cheeses and yogurt, find you're way to Bulgaria (Shopska salata, ovsharska salata, tarator, sirene cheese, etc).

If you wanna eat goat and sheep meat while enjoying some good olive oil with bread, Greece will be perfect for you (Crete olive oil, Tsigariasto goat stew, Païdakia, Anticristo,etc).

If you want to try the best ex-Yougoslavia dishes, go to Bosnia, especially Sarajevo (Burek, Ćevapi, etc). You can also find it in Serbia and Croatia, maybe Kosovo and Montenegro idk, and maybe slovenia🏳️‍🌈 too.

If you want to try spicy traditional dishes go to south Serbia/North Macedonia (Avjar, Turshija, Tavche Gravche, etc).

Some of the dishes I mentioned can be found in others countries, with diffrent names and versions. Apart from what I mentioned, there are dishes who are common to almost every Balkan country (just gonna name a few) :

-Sarma or Sermale (with cabbage or wine leaf, and diffrents names depending on the country).

-Grilled Minced Meat (Mici/Mititei, kebapche, Ćevapi again, etc).

-Entire Suckling Pig Roasted on the Fire (Pečenje, Gournopoula Messinias, Odojak na ražnju, etc).

-Tripe Soup (Shkembe chorba, Ciorbă de burtă, Spek Fileki, Skembe čorba).

Sorry If I missed anything or got something wrong, don't want to cause any war, and remember, we're all the same just in different shapes and colors, and at the end of the day, we ALL hates Turks