I don't want this to turn into a CFL versus NFL bashing session, but I would be interested in stats on how often the team leading at the half wins the game, in both CFL and NFL.
It is my guess that there are more comebacks in the CFL, but I was wondering if anyone is aware of a place that might contain an obscure stat like that?
I'm sure each league's office could give you those statistics for each year for about the last 10-15 years. Then you could see which league has the higher percentage of second half comebacks and establish which league does have more second half comebacks. One thing you have to take into account is the NFL has 32 teams, which means 16 games each week if there are no byes that week, while the CFL currently has 8 teams, so at most there are 4 games each week. You could do this by numbers, but then the NFL has more opportunities for comebacks. Doing it by percentages, if the CFL has two comebacks in one week, that would be 50%, while the NFL would have to have 8 comebacks to have this same 50% total.
You could get the data yourself, if you can get a hold of all the box scores for each game from a year or several years and just look to see who is ahead at halftime, and who wins the game. Even if one team is ahead by a point at halftime, and the other team wins the game, this would have to be considered a comeback win, the way you are defining it. I'm not sure which league I think would have more, but it would be interesting to find out.