Up to and including Jacques Delors, the EC president was a leader in terms of framing policy and obtaining coordination in its application, but that was before the end of the Cold War, massive enlargement, globalisation, and the rise to hegemony of neoliberal economic ideology transformed the EU into a government-to-government system of governance.
Actually, Delors was probably the exception rather than the rule, in being strong and decisive. Can you even name who was the EC president before him and before that? I certainly can't (but I was a kid then). So personality - and convergence of political factors at the time - made more of a difference than the way he was selected.
In fact, one could argue that subsequent presidents were selected to be not-Delors, is bland and weak and controllable by the big power which were pushed around by the Delors Commission. Wind power
I had forgotten Gaston Thorn, who was president before Delors (who lasted a full ten years, unlike his predecessors or successors with the possible exception of Barroso, we shall see...). Prodi was fairly well considered, but we were already in "constitution" badlands by then.
Barroso certainly fits your not-Delors tag.
