First off, the franchise name is Elder Scrolls, not Oblivion
Secondly, it does seem to have stolen Zelda's limelight rather neatly. I don't see the appeal, of course, but then again open-ended WRPGs have never agreed with me in the worst way possible.
I would attribute it largely to the fact that "Core" gamers (though i shudder at this categorization and wish for one better) have largely given up on the Wii, such that SS is not receiving more hype, and then you have the fact that the franchises are very similar
In many ways, Skyward Sword needed to come out sooner in the Wii's life, for more significance in the core gaming community and more impact with the expanded audience, as well as doing more to prove the ability of motion controls. The game itself was poorly positioned in terms of the amount of impact it could have had.

Monster Hunter: pissing me off since 2010.







