I'm afraid to inform you but Weekly Shounen Jump is a business. The goal of a business is to make money. Individual manga only make money when released as tankobon. Making money takes absolute and total precedent over rankings at all times. Fortunately the vast majority of series that rank well also sell well, while the titles that sell well generally poll well. When series poll poorly but sell well we have clear, direct, and indisputable evidence that sales take precedent. Mago lasted four years, had an anime, and will have additional chapters published in Jump NEXT. To Love Ru also lasted four years, was also animated, and was revived in SQ less than a year after ending in Jump. Ranking certainly does matter. Both series would still be serialized had they ranked higher. But it would be horribly naive to believe that sales were not Jump's first, last, and everything. Money talks and bullshit walks. On the rare occasions that a manga makes money but ranks poorly, sales sustain serialization where other series would be canceled.
---------- Post added at 02:29 AM ---------- Previous post was at 02:26 AM ----------
You might be reading to much into this weeks cover art. To go by the cover, Toriko is second only to One Piece. Naruto is no more popular than Sket Dance, Nisekoi, and Beelzebub. We all know that Naruto is a multi-media empire, clearly the second most popular title in Jump. If popularity could properly be judged based on the cover, then Naruto would be the second largest character on the cover.