I consider myself a "core" gamer and I'm nothing like that. In fact, I never buy games in a store anymore, I buy everything I own online at a lower price.
This way I can save money and avoid clueless clerks who sometimes seem to think they know my taste in games better than me simply based on their own preference (not you maxwell, the local ones...).
I don't let reviews dictate my purchases, I usually either get demo's, get recommendations from old friends whom I know to have roughly the same taste in games (doesn't always work out well but usually!) or I get sequels to games or installments in franchises I know won't disappoint based on past experience.
What I find almost comical on this site is how a lot of people almost feel personally offended that not everyone has fallen head over heels for the Wii, why is that so unfathomable? Nintendo made a sharp turn and some people were bound to fall off the wagon, Sony has shown this gen that it is certainly possible to lose fans and customers. (Yes, I've spewed fire and brimstone about the Wii myself but I'll end up buying one very soon... 
).
Edit; I just realized that the OP seems to try to imply that "core" gamers are actually more goaded by the market than casuals, while it is clearly the other way around, the term "casuals" in bussiness is not exactly a compliment but usually means "will buy anything we convince them they need".
