In 2009 the maximum number of suspense/thriller films released overall was 31. I think action, animation and comedy account for 52% of Box office because they are some of most popular genres. Everyone likes a good laugh, everyone likes to see things blow up (predominately males) and everyone at one point in their lives has enjoy a good cartoon. Females like a touch of romance that may attract them to a RomCom or an action thriller with a few love scene or two. This is also a niche for a younger audience. Most Thrillers that are distributed to cinemas have an age certificate e.g 16, 18. This means that however popular the film may be, there will be a percentage of people that would not get to watch it
As you can see this diagram shows us the target demo for diferent types of genres. It's not surprising that comedy is in the middle. It is enjoyed by both sexes.
Looking at some age certificates for some films see inappropriate for young people aged 15 and under