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Joelcool7, you are way off.
Mario isn't bought by the hardcore exclusively. Mario is bought by everyone. Look at New Super Mario Bros. and how well it has sold... Let me tell you right here and now that those are not 20 million hardcore gamers, those are 20 million gamers, hardcore, casual, it doesn't really matter. Everyone plays Mario.
Secondly, Mario Galaxy already is dumbed down. It's extremely easy compared to 64 and Sunshine. Loads of people will storm this topic now and yell at me about how Mario 64 only feels hard because I wasn't used to 3D Mario when it was released, but I play Mario 64 regularly pretty much every month, and it's still harder than Galaxy.
Does that make Galaxy a bad game? Absolutely not. But it is dumbed down, to a certain extent. It does have a few challenging parts, admittedly, but I can't say they challenged me very much.
