There are a whole group of arguments, but at heart we say (as labour market analysts - so that's the prism through which we examine these questions) that a university qualification helps (not guarantees) you to get the kind of job that you want (which is up to the student, and may not be 'the best paid job').
But here are some hard facts about degrees.
These are the ILO unemployment rates, as of Q2 last year.
(Level 4 are degrees).
And here are the weekly wages for England (just England) in Q2 2008
Both taken from the DCSF.
On average, a degree shows a clear benefit - it might take a while for the typical graduate to feel it, but you're less likely to be out of work, and you are more likely to earn more, with a degree than with any other qualification.
