I actually made sure to realize I wasn't speaking from a western perspective, since our perspective is unimportant (mostly) for this matter. In Japan, Shonen Jump have what they call "The Big Three" - this of course referring to One Piece, Naruto, and Bleach. They have been the current "The Big Three" since 2004. One Piece has always reigned king, slaughtering Naruto, while the difference between Naruto and Bleach wasn't near as large, but still large. In 2010 Bleach started crumbling down, and now Ichigo's face is starting to appear further back, say, along with those of the Sket Dance crew, on covers. That said, it's still part of "The Big Three", the face of Shonen Jump.
Really though, I think the idea of "picking up Jump without Bleach" is a shock for people. I remember when the anime ended. I had watched Bleach like clockwork for years, no matter how bad it got. When it suddenly ended, despite being somewhat stupid, my weeks just didn't feel right anymore. That's what I'm getting at that they are trying to avoid. Bleach has well fallen from grace anymore, but again, it has that history.
But anyway, to add numbers to this, let's put it like this: Lifetime sales of the FMA manga is around 57 million. In 2010 One Piece sold 32,343,809 volumes which was more than Naruto, Kimi ni Todoke, Fairy Tail, Bleach and Fullmetal Alchemist combined (all in their respective top ten ranks for all manga sold, not just Shonen Jump's). That's how big One Piece is, it does this every damn year. Lifetime manga sales for Naruto is 126.5 million (current volume) and Bleach is at around 82 million copies.