[Matrixbeast]

It doesn't need to be "Filler" though. Crystal presented a side story with prominence of Suicune. Emerald gave us a 3rd, completely different plot to R/S, by having Groudon and Kyogre in direct conflict with each other, instead of one of the two being entirely left out. Platinum gave us an altered universe, where Sinnoh's temperature drops and is far more snowy and icy, with the entire Anti-Matter dimension business.

B2/W2 gave us a continuation of B/W's story, except this time, there's no excuse for why the Plasma members are so rock stupid it's embarrassing.

Dream World was an interesting concept that just has too many flaws. Can only be accessed once every 24 hours? That's rather inconvenient. Can only be used for one hour at a time? Pray the site doesn't lag (Which is does). Can only bring back one Pokemon found in DW? You better hope there was only one Pokemon worth getting. Certain areas where more uncommon and valuable Pokemon are only available after reaching a certain point amount? You better hope you can find a good two hundred strangers to be friends with, then.

Dream World could have worked, but the needless restrictions put on it plus the retarded time limits prevents anyone who isn't boosting from getting anything of value from it.