How high do you think he can jump? Onoki can fly. I don't understand how people aren't getting that, not only can he fly but he can fly very fast, it isn't like Gaara levitating on sand.
Onoki is without a doubt the strongest kage. People can argue but it won't change anything. Any of the kages can beat any of the other kages depending on circumstances but some will always have a better chance than others.
Onoki - has 3 elements, (in case anyone didn't that a kekkei tota had 3) and can combine them to make dust release one of the most powerful ninjutsus in terms of destructive force, being rivaled by possibly only the TBB.
I am not counting chibaku tensei or that meteor attack because while they are powerful they don't cause the same type of damage I am talking about, they are more physical while TBB and dust release are more chakra based. If hit with this none of the five kages can survive, even Gaara behind his sand.
Probably one of the biggest factors that makes Onoki better than the other kages is the fact that he can fly, and as was noted by either Deidara or Kabuto, he can fly very quickly. The raikage's attacks are only useful on the ground so if Onoki were to take to the air A could do nothing.
Another thing that gives him steep advantages over the other kages is his ability that makes him able to fly, he can change the weight of things. He has already changed A's weight and has done it to Gaara's sand, so it is very obvious that he could use that to his advantage in battle. If he made Gaara's sand ultra heavy then it would also be much slower and consume much more chakra from Gaara. If he used an earth clone and did this to A then he could make A either super light so that his punches do no damage, or he could make him super heavy so that he can't run quickly, if at all.
Onoki also seems to have large chakra reserves, as he has been fighting very high level people nearly non-stop for a while now.
Mei and Tsunade have almost nothing they can hurt Onoki with. Tsunade can't fly nor can she withstand dust release and her summons is too large and slow to be able to dodge dust release.
Mei has two KG, but if Onoki is flying then her abilities are useless against him, and she has shown no speed feats to be able to adequately dodge Onoki's attacks.
Lastly Onoki has a very strong defense of stone golems that he can use to protect himself from large scale attacks.
So while it may be true that each of the kages has a chance against the others, it seems obvious to me that Onoki is the undisputed strongest of the current kages.