I don't think he's greedy as such, I think it's just that he knows he has more to prove than any other striker on the team, and has been in that situation for the last 2 seasons. Think about it, whenever Keane was injured last season or the one before - i.e. when he was 3rd choice instead of 4th - he's been much more the 'sharing striker' type you're after... because he could be. It didn't matter if he got goals then, he could guarantee being selected for the next game. Keane and Berb have that luxury now, so they can afford think more holistically about it. Bent's the same as Defoe, the difference being that there's no quality there.
As for loyalty - couldn't agree more Rambr0. I think the obvious argument is that we're his best chance of winning anything (before anyone disagrees, we're still in 3 cups, and - let's be honest - the UEFA cup should be the easiest way for any team outside the top 4 to get silverware), but I really believe he'd rather have a career than a medal for benchwarming. Yet he's still here. To me, that's loyalty.