why did cartoon network cancel the othersiders?

Because CN Real programming block was expired after the end of the summer of 2009, but the I don't know if the Othersiders will be coming back on Cartoon Network or not.

Well...... I actually watch English-subtitled Japanese anime, so I think I know why they canceled Naruto. In Japan, they've released the new part called Naruto Shippuden, which is basically just Naruto three years in the future (so we don't have to wait for Orochimaru to take Sasuke's body). In the United States, of course, that isn't out yet. So I think why they canceled it is because they are WAY behind on animating Naruto Shippuden (they said they'd do it like in February or something -_-), so they're holding back on the last episodes of Naruto. As soon as they feel confident in their animated version of Shippuden, they'll continue airing it again. Another reason could be that one or more of their main voice actors quit or they realized how long exactly the Naruto series was; so they gave up. Why they won't air those last few episodes of the original Naruto series, I have no clue, but hopefully someday in the future, they will. ;-) Hope this helps!