People from all over the world go to the park, just as people do at WDW. You have not only Universal Studios, but Islands of Adventures, the first part of The Wizarding World of Harry Potter, soon to be second part of the Harry Potter park, and the City Walk. If you truly want to experience the whole package you couldn't do that in one day.
Anyone can have their opinions on which park is better, but it seems as if most people who dismiss Universal seem to only judge by assumption, or what they've heard rather than research it, or experience it themselves.
Islands of Adventures has been the theme park mainly advertised as having the "thrills", not Universal. People always make it sound as if Universal has always had roller coasters, when it has been Islands of Adventures. Universal didn't have their first roller coaster until 10 years ago (been opened for 24 years). Either way, both parks have changed dramatically over just in the few years, not only their rides, but their themes, and compared to the whole decade have changed even more so.
Universal/WDW will always be different from each other. Some people prefer Disney, some people prefer Universal, some people like both such as myself. And as other people said, you can't compare the two. However, I do not understand why some people have to talk down Universal since they advertise as being more "thrilling", or people say there's nothing to do there.