I can't think of a reason why C2 couldn't be used for hugely successful games like SpaceChem or Braid, but the truth of our current state of affairs is that virtually all of even C2's best games would fall into the above-average hobbyist range
RandomExile: Braid took Jonathan Blow 3 years to make on his own, as a full time job.
C2 is 2 years old, and some of the features (like Functions) are less than 6 months old.
Do the maths from there.
On a personal note, I found myself realizing I have much troubles working on the very same project for long extended period of times.
After a month or two, I have troubles keeping motivated in the project and find myself toying with new prototypes/ideas.
For games in that scope, C2 is just excellent.