Hi, I will vote for Macedon as the best Greek faction.
To me they seem to have the best all rounded army, their cavalry are decent and the royal pikes are reliable. Macedon's starting position is also so extremely good, their cities are nicely clumped together in one of the most profitable regions of the map.
While the Greek cities have good soldiers in the armoured and spartan hoplites their cavalry is lacking and it forces you to put multiple generals in an army to have a good cavalry contingent. I find their starting position to be relatively weaker compared to the Macedon, their cities are too spread out and you end having to fight on multiple fronts just to defend what you have. Having a city on Scicily also forces you to fight the Romans quicker than you might like.
Thrace I find to be extremely weak, their infantry roster is poor, they don't have any elite infantry that would allow them to have presence in the late game. Their cavalry roster while being mediocre is also very small, you cant even make up for this by putting a lot of General's in an army as their General unit is also one of the worst in the game. Their starting position is nothing special, its a bit out the way but you will be attacked by much stronger neighbors.
As for the selucids, I know their unit roster is actually very strong if you are able to survive the initial battles with your surrounding factions. Overall I couldn't vote for them as their starting position puts a massive strain on them. In every campaign I have ever played, they have been destroyed fairly quickly.
I have not played the game for that long but I did hope to contribute something.
[This message has been edited by Mr Wonka (edited 08-26-2012 @ 06:50 AM).]