According to 3D World Magazine, based on installed copies, the list below is what you get (from most installed at the top):
Hash Animation Master
Electric Image (EIAS)
Toon Boom Studio
If you are looking for the top animation software packages in terms of professional users in the Television and Film industries, I would have to say (and this is my opinion - I hope others weigh in on this):
The above are not ranked in any order, they are just the packages that I would consider professional level and rock solid in terms of feature set.
Good luck with your assignment. Given the changing nature of the industry, it's tough to call the top players in any order. I've never heard of some of the packages in the first list (and some, such as Flash, I don't consider 3D programs), but I'm a 3D Studio user, and all of my time is spent trying to stay on top of its' features.