Completely didn't happen:
Copley Square Tower
One Bromfield
Aquarium Garage
Parcel 15? (originally proposed mid 600's, then mid 500's, then cancelled)
Notably cut down:
North Station Residential
Winthrop Square Tower
That's 4 600 footers that were completely unbuilt, another that got cut down under 500', then Winthrop that was cut from 700's into 600's. Basically half of the high-impact towers didn't happen or were cut down.
Mission Hill had 400'+ proposed, but cut down to like 6 stories. Fenway/Kendall has a trio of unbuilt 300 footers, including the air rights project over the pike. Kendall had hopes for 500'+ that aren't going to materialize. North Point is the most disappointing result in the history of the Boston area.
Overall we got about half of what we should have from a skyline perspective. I do agree that it's a miracle and a revelation, especially because of how used to disappointment we've been for so long, but while it could have been so much worse it also could have been quite a bit better.