In gameplay of course they're going to be similar - all turn-based RPGs are. If thats your argument you might as well say all video game RPGs are rip-offs of table-top ones (see Dungeons & Dragons for instance, which is balanced around a four-character party using a turn-based combat system and has been since the 1970s) and be done with it. Now, even in that regard the Djinni do set Golden Sun apart by supplying a unique way to improve character stats, change classes, and providing a unique source of attacks as well - they have those uses in addition to their ability to do summons, you'll recall if you've actually played the game. But in any event gameplay of the character's game isn't even close to relevant when it comes to considering characters for SSB.I'm not gonna write a book just to explain it to you... the battle system is very similar, you have a party of four, etc, etc, etc... storywise is not the same thing I meant gameplay.
Anyway, since its my first post here I may as say, although my signature gives it away, I hope to see Isaac in Brawl as well. I'm a fan of Golden Sun and hope to see it and several other overlooked Nintendo greats get represented in Brawl, and of course Isaac is the clear choice. Plus it'd help give Golden Sun more publicity, and thus more chance for a sequel - I'd love to see it join Fire Emblem as a long-running Nintendo RPG series, though of course thats a more far-future (and far-fetched) hope.
Zevox