In part, I do agree will you, happy episodes are entertaining. But there isn't sufficient material in happy episodes, thus Hasbro will run out of ideas, making the show end.
I, for one, loved the episodes with conflict. Remember the Discord episode? The conflict was what I loved. How the ponies magical pure land was overrun by the forces of evil and destruction. Where Fluttershy lost her kindness, where Rarity lost her generosity, where Applejack lost her honesty, where Rainbow Dash lost her loyalty, where even Pinkie Pie didn't want to smile, smile, smile. Where the ponies lost hope. It was quite entertaining.