Rijkaard won stuff when he had the best team in the world.
Can he win when he doesn't have the best players? Can he win without Ten Cate?
This is a fair comment. However, it should be noted that more than a few of those players who formed that "best team in the world" were brought in after Rijkaard had arrived.
He was definitely quite involved in the selection process for those acquisitions, which for me, is incredibly important (although much easier to do with Barca's bankroll). Obviously there were also some very talented youth players coming through the ranks at that time that responded well to his tutelage - highlighted by the Messi monster - but I think we've got some promising youngsters that he would enjoy working with... and the cash will be flowing a little more freely again, once our stadium comes into play...
Edit: Forgot to touch on Ten Cate, but you're right, he was clearly a considerable asset to Barca, and his influence should not be undervalued.
I think that was demonstrated again last year, at Chelski.
Plus, we are talking about replacing Ranieri, right? I remember watching that CL final against Arsenal with one of my best friends and his brother (both hardcore Gooners), and Rijkaard's subs in the second half really did help turn that match.
Can't really imagine such impressive moves from Ranieri, a guy who brings in Marchionni and Grygera when we desperately need goals to save the season... meanwhile Gio and Trez are wasting away on the bench.