Millennium Tower? - Maybe, if you ignore the unfinished roof, which from many views is hard to ignore...
1 Dalton? - The tower itself is better than the location or the ground level. Loses points for still being unfinished, and the lack of lighting. But... probably? From the West it blows my mind.
Bulfinch Residential? - I don't know about great, let alone truly great, but it's definitely solid and a relatively original design/facade treatment.
Hub Office Tower? - Too soon to tell, but truly great is a stretch and a half. I think it will be pretty good.
Winthrop Square? - NOT GREAT.
Bulfinch Office? - Certainly has potential to be great.
South Station Tower? - NOT GREAT.
In short, maybe Millennium Tower, probably 1 Dalton, likely Bulfinch Office Tower.