That's not really a Bad thing, I mean it happens all the time that plots get recycled. Only, in the old days, it would take a decade or so. Maybe a Century. Seems like the Japanese are getting a jump on cultural recycling...
It has other elements, so it's not an outright rip off. I actually think that this is what they ere trying to do with Gundam: Seed, only here, they do it successfully.
Besides, there are other shows that do the same thing, and they're okay. Popular, and also with a coherent and enjoyable plot.
Take Narootoe [sic] for instance.
Facts:
Main Character is an orphan, outcast by society, and bears a strange mark. But he has strange and inexplicable powers...
Around his eleventh year, he is accepted to ninja [wizard] school, where he learns jutsu [magic] and makes friends.
Eventually, the underlying plot is uncovered, revealing the main bad guy, who:
1. Was Sealed away somewhere.
2. Is seeking Immortality.
3. Has a snake fetish.
There are quite few more parallels, and also some significant differences.
I'm not a diehard fan, but I can watch it when it's on and not fly into a rage.
Which is more than I can say for some other shows...