With Late Registration, he brought Hip Hop, musically, to a place where no other artist has...go back and listen to the live instrumentation, (Jon Brion), and listen to the arrangements, listen to the way he chops and sequences his samples...not many people pushing the envelope in that direction as much as Kanye IMO.
Hate him or love him...there aren't many people who care about the musical aspect of Hip Hop as much as he is...
It takes a certain amount of humility, especially in the world of Hip Hop, to call in another producer to help with YOUR album,( Non-Hip Hop at that ) in hopes of making the best music possible.
And at the time where synthesized beats were prominent in Hip Hop...Kanye, along with Just Blaze, brought sampling back to mainstream Hip Hop IMO...they made it 'cool' to sample again.
You can hear the influence that they've had to this very day. Another thing Kanye is doing is helping bridge the gap between mainstream and 'underground' Hip Hop...I can't think of any other artist in Hip Hop besides The Roots who are doing that.
Just my .02, but I think Kanye is great for Hip Hop
Oh yeah...and about the cockiness...rappers have been cocky and boisterous since day one, its part of the appeal IMO...they probably don't always mean it literally, but what it does is get people looking in your direction.
And like they say...all publicity is good publicity.