On the G distribution map Macedonia is well represented with a quite high level of G the very surprising thing is to found in Macedonia the famous G2a3b1 DYS 388 =13 found in Northern West Europeans ! Are you listed in the FTDNA G project ? Anyway the ancient Macedonians who came to Greece were surely G men as may be Alexander the Great called also the Macedonian ...
G haplogroup from Slavic settled area (Former Yugoslav republic of Macedonia + areas in north Greece above G hotspot) might also be due to some remaining group of Alans that are likely to have arrived with Macedonian Slavs...
hotspot of G related to ancient Macedonians is bellow Slavic settlements...
based on the position of the hotspot my guess is that ancient Macedonians have lost their identity and were completely hellenized..the name Macedonia stayed as geographical term, and Slavs who settled in province of Macedonia (which actually fitted more to ancient Peonia) eventually accepted geographic term Macedonia as their own ethnonym...
and no, ancient Macedonians were not exclusively G2a... they also had some other haplogroup since hotspot of G2a doesnot go over 12% in areas 21 and 23 that are clearly related to ancient Macedonians
in paper:
http://www.familytreedna.com/pdf/italy.pdf
(btw. Figure 1 also clearly separates ancient Macedonians from Greeks)
looking at the table I would say they had large R1a, E-V13 and I haplogroup(probably I2a2)...
so they might have been one part of R1a wave that arrived to Europe, while large G indicates that they did dwell a lot somewhere near Caucasus before doing so... and E-V13 is probably related to Thracian Illyrian and Dardanian influence..
R1a there probably dominantly does not origin from Slavs/Serbs since R1a is there in significantly higher percentages 25% and 20% than among neighbouring Slavic populations
and I being 20% and 12% might be influence of Serbs (also very high in Macedonian Slavs that are often considered to be south Serbs who were dominated by Bulgarians and developed language somewhat closer to Bulgarian than to Serbian), since in nearby Serrai area that was Serb stronghold in 14th century (last settlement was thus done by Serbs in 14th century, since later came Turkish empire and Turks didnot massively settle those areas) it is 36% which is alike to levels in Serbia...
in fact Serbs initially settled in a place Servia in area of ancient Macedonia... where hotspot of G2a is, but they didnot stay there...
http://en.wikipedia.org/wiki/Servia,_Greece
so, haplogroup I might be signature of Serbs there, though it may have also been present in ancient Macedonians...
thus, ancient Macedonians were dominantly R1a and G2a and E-V13 (and maybe I2a2)
and before moving to Balkans they probably did not carry E- V13
I would say that G2a, I2a2 and R1a pinpoint to their iranian origin..
I am personally inclined to see I2a2 there as native to ancient Macedonians, because of ancient legend of Queen of Sheba
Queen of Sheba was also known as Makeda in south part of her country (similarly as south of Serbia is Macedonia) and she was known as Balkis in arab countries...(as Balkan got its name during the rule of Ottoman empire that was under the influence of Arabs)
http://en.wikipedia.org/wiki/Queen_of_Sheba
for me this is clear ancient relation of names Serbs, Macedonians, and Balkan...
and ancient Macedonians might have been early offshot of iranian Serbs
iranian origin coupled with wide spread of Serb tribes in Iran (e.g. today Pashtun Serbans and Kurds are probably branches that origin from iranian Serbs as attested by similarity of names and by hotspots of haplogroup I in both Sarbans and Kurds) allowed Alexander Macedonian to do quick conquer not so much by battles as by trying to unite iranian people in single kingdom... how else could tiny ancient Macedonia spread so fast so far away?