Toriko doesn't rank low in any way shape or form. It's been #1 on the Jump TOC for 3 weeks running, got 10th most sold manga of the past 6 months, and has been constantly getting 6.5+ ratings in the anime, making it like the 7th or so most popular anime out there. And definitely the highest viewed one this season. Though that has a lot to do with its time slot being right before One Piece.
Actually, last week's rating was a 7.8, which is a lot higher than it's been. For reference, One Piece is about the third-fith most popular anime in ratings and it ranks around the 8.0-9.5 range usually.
Besides which, Toriko is far from a kiddie series. Even if it has some gags, it goes a lot into science and nature and the like. and has its own pseudosciences. It's pretty adult by most Shounen standards. The beginning of the series has less of a serious air to it, certainly, because Toriko's mostly just playing around and rarely gets serious or has his life threatened.