Did ancient Greek & Roman styles of wine tend to be sweet ? (I looked around and found one site/cite at the Egyptian museum online which suggests Egyptian types were, anyway.)
Check the Oxford Classicial Dictionary on this subject. They have good information on this subject.
Off the top of my head, I would think that a lot of it would be totally awful by today’s standards. This is mainly because it spoiled quickly without the quality of bottle-sealing we now have. So there is posca, which is apparently the semi-vinegary/vinergaized wine that the Roman enlisted people were given and which is probably the “gall” offered to Jesus on the cross.
The OCD mentions that on one island in the Aegean, the flavor of exported wine was “improved” by the addition of seawater. I also believe that spicing wine and flavoring it with honey was not an uncommon practice in the old days.
Retsina is a Greek white wine that is very dry, and not very sweet, which is currently available. It also has the distinction of having pine resin added to it, and like Oouzo is an acquired taste, at best. Reputedly, this stype of wine is very ancient, and the reason for the pine resin flavor is to simulate that which one would have tasted from back in ancient Greece, when one would have drank wine from amphorae that were sealed with pine resin.