Jealousy is obviously the source of this hate in most cases. For the same reasons people hate on games like Halo, both series just won't stop selling.
Here's what probably goes through their minds: "How can they release game after game each year without actually experiencing a significant decline? Why must we keep coming up with new IP's while they can just re-release the same games over and over again while their ignorant customers keep buying them no matter their content? They were lucky to come up with that specific franchise. Until they have shown that they can create new successful IP's (casual ones such as Brain training and the Wii series obviously doesn't count), they shall forever be known as cowards."
Another possibility would be that they really want to love Nintendo for whatever reason but can't given their current existing IP's.
