For a game that got lil' to no hype or advertising Zack & Wiki didn't bomb. On the level that both are great games I see the comparison, but with the ad push for LBP, if it sales within the range you mentioned, which I think it will too, that will be a harder pill to swallow.
The Interweb is about overreaction, this is what makes it great!
...Imagine how boring the interweb would be if everyone thought logically?