I think the insanely focused attention the first month (or week) gets is just not good analysis. Word of mouth tends to spread more on market leading consoles.
Guitar Hero is a good example, because most people thought that game flopped in it's first month waaay back in 2004. It just kept steadily selling on word of mouth alone until a franchise was born. Pokemon is another good example, as it totally tanked in it's first few weeks in Japan, but just grew and grew and grew and now it's the most popular RPG ever.