In Ken Dryden's/Mark Mulvoy's 1973 book entitled Faceoff At The Summit, an interesting statistic was published: Shots at goal. Although no definition was given, it is safe to assume that shots at goal included actual shots on goal, as well as shots that were blocked, hit the post or cross bar, or went high and wide. Essentially it is a form of measuring scoring opportunities, although it would appear that a good scoring opportunity that did not result in a shot attempt is not counted in this statistic.
Below are the statistics and some calculations. Scoring %: Actual Shots is obviously based on the amount of goals scored based on actual shots credited, while Scoring %: Opportunities is based on goals scored vs. shots at net. The Shots on Goal % examines the likelihood that an attempted shot resulted in an actual shot on goal
You can also view individual player shots on goal and shots at goal here.
And you can view game by game scoring opportunities here.