Deidara's attack on Sunagakure showed excellently how many more capable Shinobi there are in the village who did not become Kazekage because Gaara (who is practically Mary Sue at present) had to be controlled.
As I said, it is an indictment of the village that they have no good Shinobi except Gaara. Incidentally, it was also an indictment for Gaara. Sure he had the disadvantage that he had to protect his village, but the battle fort was ideal for him, a lot of sand. Deidara, on the other hand, was disadvantaged because of the place, because he didn't have enough clay and because he wasn't allowed to kill his opponent, i.e. no C4 and C0. How does that now raise him above the other Kage?
Just as his address to the united shinobi army showed how incompetent he is as a kage and leader. Even the Nidaime Mizukage was clearly of the opinion that Gaara should never have become Kage. : /
The address was probably ridiculous. Wouldn't have missed much and he would have howled around at the end. Just sentimental talk with no real content. That shows least of all that he is a Super Kage.
I don't think much of A but what he said to the Jinchuriki, what he would do to win the war and save the world from Madara THAT was worthy of a Kagen and really mattered.
To Shisui Uchiha: But not wiser either. Because of their age, they too should be equally smart, but the quality of not acting based on emotions has to be emphasized even under Kage when looking at A and Tsunade.
As I said, this is still not a unique selling point for Gaara compared to Mei and Oonoki
The three other elements only bring a real advantage against sand in the case of Meis Suiton and this must also be very powerful in order to take on Gaara's sand mass.
Mei doesn't need a suiton. Her KG should be much more effective.