Yes, it is a genuine horror/thriller. Actually, an interview stated that the main reason the film is keeping its title is because Samuel L. Jackson is fighting hard to keep it that way... and I hope it stays haha.

http://entertainment.news.com.au/sto...4-7485,00.html

However efforts by executives to change the title to something more mundane, such as Pacific Air 121 were stopped by none other than lead actor and screen legend Samuel L. Jackson, who refused point blank to see the title altered in any way.

"Snakes on a Plane, man," said Jackson during a recent interview with Collider.com.

"We're totally changing that back. That's the only reason I took the job: I read the title."