Usual power scaling put Makarov above Gildartz. Just see the fight against Acnologia in Tenrou, Makarov could at least hold Acno for a few secs eventhough heavily injured while Gildartz looked completely powerless. Mak problems is that Mashima usually throws in convenient health problems to him to take him out at the right time, else he wrecks. He also have others crazy feats like being able to tank Jupiter Cannon with bare hand while the same one sent Erza flying in her strongest armor suit and left her unconscious for a while.
Under Gildartz there are Laxus/Jura (gap very close), with Jellal stands in the middle due to the lack of feats for Sema and Abyss Break, probably can go even higher when he gets the major fight of the arc which is kinda certain to happen.
Gildartz also kinda lacks feats. We still don't have full explanation for his magic, even he admits himself that he can't fully control it. He also lacks some speed feats and versatility in general (kinda like a one trick pony). Dude also isn't that intelligent IIRC, so there are still possible ways to take him down with the right combination.