I've just been reading through some of the manga and started at the links some of those guys posted in the Naruto Forum. Rather than actually destroying real planets it seems they fight by attacking each others cosmos or each others personal universes, which would be another way to think of it. If you actually look at the real destruction caused by their attacks it's actually not very impressive at all.
Someone keeps posting scans of someone causing an explosion and wiping out loads of planets, but since when are planets ever in such close proximity in the first place? All the planets shown in that scan were pretty much on top of each other. Then a few scans later on we see that the place they were fighting on has actually received very little damage.
It seems people who are making a case for the Saint Seiya being galactic and some say even universal in scale is based upon statements made by the characters in the manga but if you look closer as to what's actually going on they're not talking about real life events but rather events created with their own pocket dimensions.
I mean lets just look at what is probably one of Hades greatest feats, re arranging the solar system. If these guys really were galactic level busters wouldn't it have been easy for them to move all the planets back into their original positions. Do people not understand how much larger the galaxy is than the solar system? Anyone at a galactic level should be laughing at such a small feat as re arranging planets. Even someone who was at star level would laugh at such a feat.
That's my two cents using about half an hour of reading through the manga. If someone could provide genuine evidence without just providing scans and not explaining them whatsoever and then crying when someone makes a counter argument then I would gladly look at them and consider them.