Again, MH4 DSs were sold out within 24hrs of their announcement, unless you went in there the day they announced it they wouldn't have been able to help you anyway.
As for Amiibos, it's understandable to be mad if you had no idea how popular the little buggers were but because of their limited supply and fanatic fans, again unless you camped the store there's little way you could have gotten them in the first place and thus no real way for GameStop or any retailer to help you.
I'm all for jumping on GameStop when they provide crappy service(which for many people is often) but this is a moment when the blame should be on Nintendo for their extremely detrimental supplying choices.
They did make more monster hunter NDS
Except, instead of gamestop announcing it to the world to be bought out by scalper bots to sell on ebay for 10x the amount, they did region in store only purchases that you could only buy 1 of. I think this was a brilliant idea, and I hope they do this from now on for highly anticipated products like the monster hunter NDS.