Indeed, that is how your arguments sound: "We had wars and sanctions, you were free of such troubles, but nevertheless now you are in the same bog like us".
I'm afraid you will be dependent on the will of the larger European powers even with standard of living as high as the standard of Luxembourg. Between the medium (like Serbia and Bulgaria) and the largest European countries there is a drastic disproportion of resources and this situation won't change in the near decades. The political consequences of this fact are obvious.
I don't think that the Baltic countries don't have strategic importance for EU - they are a barrier against Russian influence in Central Europe, they are too small to resist to Russia alone. I don't mean any kind of drastic confrontation with Russia, on the contrary, it is a strategic European partner, but EU Baltic policy is a measure against its economic expansionism and appetites for restoration of its political positions in all the countries of the former USSR. Still more, from the perspective of NATO interests the Baltic region is a spearhead, stuck on 800 kilometers from Moscow.
By the way, the importance of Serbia as transport corridor will decrease after the completion of the European transport corridor 4:
http://en.wikipedia.org/wiki/Pan-European_corridors
The routes from Istanbul and Athens to Central Europe will pass through Bulgaria and Romania as well, the distances are the same, but they lay entirely on EU territory without border and custom barriers. The building of a new bridge over Danube near Vidin, part of the Corridor 4, is making rapid progress:
http://www.danubebridge2.com/en/
I don't want to offend you in any way, but I think that the myths of our Balkan "strategic importance" are nothing more than national romantic exaggeration. Serbia and Bulgaria are not irreplaceable in many aspects. See the project of South Stream Gas Pipeline for example - Russia could built it through Turkey and Greece or through Romania and Hungary if Serbia and Bulgaria refuse to accept some of the key Russian pretensions. The same is with EU on its way to Turkey and Near East beyond it - there are routes through Croatia, Montenegro, Albania and Greece and Romania and Bulgaria, which exclude Serbia. I think we have to be more realistic and we must not act as "European powers" or even "leaders of the region", the second is a permanent Serbian self-delusion.