Missed too much to try making direct quotes, so I'll just try to get to the highlights....
Djiin offer large amounts of character customizations, allowing you to pick which abilities, stats, and roles you want your various characters to fill. Many, many customizations options.
System is well balanced because the strength of you classes can only be maintained by freezing use of your best special abilities (Djiin attacks and most damaging attacks (summons).
Calling Golden Sun a "typical summon system" is absolutely absurd, it actually one of the few games that actually justifies summons by making them a central point to the battle system, and materially distinct from your regular magic.
The relationship between class/djiin/summon is a complex, multilayered system that self balances on several levels the way very few RPGs even attempt (even many of my favorites, such as VP or Grandia, which I enjoy more for the different kind of battle system, fall short of Golden Sun in this regard).
Very few people have attempted to deny this, because it's pretty hard to deny without making yourself look like an idiot (particularly when you've just spent the morning praising shallow-ass games like Mario and Luigi). So instead, the more common argument is to sidestep the issue, by saying that the game's depth is irrelevant, because the game is too easy for it to matter.
This is also really stupid.
Partially because there's a vs mode for battling in a level-nuetral zone. Partially because the game has a lot of optional bosses to add extra challenge. But most importantly because The Lost Age is a game that gives the player a very high degree of control over his levels. Random encounters are very easily evaded. I can get really overpowered in Valkyrie Profile and Tactics Ogre too, if I want. It doesn't mean anything. The ability to utilize the strengths a game's depths is far more relevent than the ability to neutralize them. In some games (FF5, FF6), you can't see this unless you really go out of your way to literally run from every fight in the game. But it doesn't take much in The Lost Age. Plus, not fighting those battles means more time to enjoy those slick dungeons!
Generally, the I consider the components of a good RPG to be-
Intersting/unique battle system
Variety of abilities and customization options to use within battle system
Balancing variables to prevent unqualified exploitation of said abiliites
Exploration + discovery (dungeons or overworld, either way)
Puzzles
The ability for the player to consider the extent to which he would like to focus on these.
The first is the only criteria The Lost Age does not meet. I can think of very few other games that do as good of a job overall. (of course, there's a lot of degrees to which a game can suceed in these categories)
Also -
The lack of carryover targeting is a good thing. When we're talking about how well a game plays, a condition which forces you to be more thoughtful with your decisions is good. The ability to just watch TV while mashing the A button is bad.
The story isn't good, but this is should only be relevant for the followers of Konex.
it really is Pokemon all over again.
Oh man....berating Golden Sun is one thing, kinda tolerable in some respects...but please don't tell me anyone tried to call Pokemon shallow; that's just over the line....