Jedi's don't destroy planets, thats what Sith would do obviously or Dark Side Governments like the Galactic Empire.
http://starwars.wikia.com/wiki/Galac...re#Astrography
The Galactic Empire's territory at its peak consisted of some one and a half million member and conquered worlds, as well as sixty-nine million colonies, protectorates and puppet states spread throughout the entire galaxy, stretching from the borders of the Deep Core to at least Wild Space.[14]
The Galactic Alliance was the same size in term of the 69 million figure which probably reached up to 80-88 million because the Tion/Hapes/Chiss were members but they had 1.2 million member worlds, the extra 300,000 planets were probably worlds "conquered" during the Empires reign.
The most recognizable symbol of the Imperial Starfleet was the Imperial-class Star Destroyer, which peaked at over twenty-five thousand vessels,[10] although millions of starships of different designs were fielded for various purposes.
Super Star Destroyers became infamous for their size and armament, but some also contributed to the fleets as logistics vessels[11] and starfighter carriers.
There is also another reference on this Wookiepedia of the GE being this large but I can't find it, that was a mistake because the 25,000 Star Destroyer figure comes from the Galactic Empires "Conquering" fleet, the Millions of ships were part of their Starfleet, the Galactic Empire did not need a very large conquering fleet because anyone who could challenge them would loose anyway, any extra galactic power challenging them with millions of ships would loose, they would simply call the Starfleet for back up.
Plus it is important to streets we are talking about the GALACTIC ALLIANCE here , not the Empire, I am only referencing the Empire because these are the only sources that exist for these numbers. Considering how the Galactic Empire was practically the same in size to the Galactic Alliance then it is only logical to assume that they also had these massive warfleets. They had even more because the Imperials developed a stronger Navy/Starfleet then the Alliance during the Victory without War program and probably had 20% more ships then the Alliance did since they lost more support due to the Sith manipulation which eventually turned into a major Galactic War.
Still the in the current continuity of Star Wars, they are now rebuilding after defeating the Sith who casued a division within the Imperials with many Imperials choosing to side with the Sith and other staying loyal to the much more benevolent Fel Empire who never did conquer other worlds by aggressive means and would only wage war in defense, they didn't even take part in slavery, the Alliance did, they were even nicer then the Galactic Alliance they were members of.
A New Galactic Federation Triumvirate is now formed but if you went back in time, obviously the Large Galactic Alliance would ruin the Imperium simply by over-running their Navy which is inferior in size and strength (since the most powerful Alliance/Empire ships are stronger then a Emperor Class BattleCruiser)