Let me however try to give me a feel for why Peel was a much-loved figure in music. First, he's been on the modern (Beatles onwards) pop music scene for as long as that scene existed - in fact he used his Liverpudlian connection to get himself a job in the States on the back of the Beatles' success at the start of his career. He genuinely seemed to love all music that had been created with a passion, right from Belgian nosebleed noisethrash mp3s through to jazz standards recorded on crackly 78's. His Radio 1 programme would typically showcase both of these and everything inbetweeen. His links were usually extremely witty and peppered with little anecdotes about the band whose music he'd played, or some little story about how he came about purchasing that particular bit of green vinyl from a backstreet record shop in Groningen. Even as he was starting to draw a pension, he was still producing two hour shows three times a week. The consequences are severalfold: (i) he gave people who tired of the formulaic easy-listening pap that makes up most of a radio station's playlist a refuge where something more challenging could be found (but without taking it too seriously like what more eclectic programmes on R3 do); (ii) this exposure to a wider range of music (such as, I understand the DIY ethos of the punk movement) inspired many people to start making music themselves (see the tributes passim); (iii) it also gave budding musicians something to aspire to, viz getting Peel to give them a session and help get them noticed (if they were any good); (iv) it also created the impression that he would always be there, one of the reasons why he is sorely missed.
It's impossible to know how different the pop music tapestry would be without him; but I think it's wholly appropriate that he should be saluted for having made a huge contribution to the particular way it came to be woven. I think that's what people mean when they say he's a 'great of music'.