Are you kidding?
Look at what Rolling Stone thinks of him:
Jay-Z | Bio, Pictures, Videos | Rolling Stone
Or when MTV put him down as the GOAT:
MTV.com: The Greatest MCs Of All Time
Jay has headlined festivals and had sold out tours throughout the world, it's clear many people rate him as one of the greats, but in terms of what he's actually done for hip-hop, not what he's done for himself, Cube > Jigga.