I can't think of a single generation that was bad.
I mean fuck, Gen 1 started everything, Gen 2 added Steel and the special stat split, along with Scizor, Skarmory, and Steelix, as well as breeding. Gen 3 added mother fucking Swampert, Shedinja, the cover trio, weather, a cool as fuck region, natures, and a new IV EV system iirc. Then Gen 4 added the physical special split, Garchomp and Toxicroak, a ton of other cool Pokemon, and Cynthia. Then Gen 5 added a shit ton of cool new Pokemon, hidden abilities for old and new alike, and Volcarona, and now Gen 6 has added an 18th type, rebalanced the type table, made EV training and breeding a cinch, has much, MUCH improved online functionality, and a waifu maker.
A WAIFU MAKER. Fuck you bickering shit plebs.