Being a member of the customer service industry, such harsh opinions are best kept to themselves instead of providing it to a potential customer for such reason. Depending on the manager, such "rants" would cost the person their job because...
A) Offending the Customer -- One NEVER disses a product. One may express their displeasure with a product, but must do so in a civil tone. "I never got into the Pokémon series myself, but <game mechanic> reminds me of <preferred game>." While it does note some dislike for the game, it does offer some potential options for the customer to consider. HOWEVER, one of the golden rules of customer service is to keep any negative comments to yourself.
B) LOST PROFIT -- Just like reason A, you lose money for the store... not just for that sale, but potential future sales from that person for that bad interaction. It might be a $40 lost today, but when they choose to buy their systems & games elsewhere, that loss amount increases quickly... especially when new systems are released.
If the manager was in the store, that employee would be at least written up... if not fired on the spot (depending on the manager & the infraction). However, as you didn't escalate in the store nor get a business card to notify the manager, there's really not much that could be done at this time (as time is of the essence for these issues).