Firstly, I won't talk about degrees per se, but the environment in which you achieve the degree. In college/uni, you are given the opportunity to absorb a lot of knowledge, meet with experienced professors personally make aquantinces with a lot different kind of students, have access to laboratories and do your own research, etc. Besides that, there are societies and clubs to join as well. By joining those, you can learn to do things that are beyond or not in your degree syllabus, like organizing events, being a "treasurer", designing posters, meet with outside people, represent the uni in sports and so on.
Its the combination of all of those that would make a degree as something beneficial. But, a degree are useless if you dont take advantage of the process of getting it. If you are a lazy bum who skips class and aims to get the pass, then whats the point? Even those a straight 4.0 students who just seal themselves up at the study table may lose out.
Secondly, "sucess" itself is a matter of personal definition, as reachrkata said. Whether you want to have you own business, invent a new device, discover a new law (or flaw, in reachrkata's example), be an actor or a basketball star. Some generally define them as success because in the end those people get rich. However, how about those who seek to solve the world's problems, help people in charities, be a soldier defending your country, a policeman keeping civil order and a teacher spreading knowlege to children amongst other things? All are considered a success. So money isnt really everything if you want to consider what success is. Some require degrees, some dont.
In conclusion, you dont always need a degree to be successful. But that only depends on what you want to be successful
in. How you obtain the degree can also decide the avenues of what kind of success is possible. Thats it for now.. maybe I can add some things later if this debate goes on
