I think in the wake of the pedophilia allegations we often forget how absolutely massive Jackson was, and whether you despised the man or you would let him babysit for you, his music was tremendous and the defining sound of the last quarter of the twentieth century.
Carlin is undoubtedly a big loss but like my hero Bill Hicks his message will live on in his fans, and Cronkite can't be undervalued as one of the finest journalists to have lived. While it is always difficult to lose important figures, as much of a legend as Mays was, he's a pop-culture icon more than anything else.
Jackson's music, for me, makes him a bigger loss, but undoubtedly everyone mentioned in this conversation has contributed a lot (save Mays, although I'm saddened that there will be no fresh YouTube material for us UK enthusiasts of loud and enthusiastic sales techniques)...