Yeah, US charts can definitely be misleading and are sometimes exaggerated. Japanese charts don't factor in enough information and are set up kinda odd. I only know a little about other charts, but not enough to say anything about them.... But I'm sure they also have a decent amount of flaws. It sucks, but that's how it is, I guess.
Honestly, if ORICON starts to count digital sales, I think they'd easily be my favourite chart. But, in their defence, it's hard--make that impossible, to have a perfect chart, or to always have it consistent, even.