C. Gen.1's are nostalgic, but mostly pretty lame. Gen.2 had some greats, but also a lot of the s****iest. Gen.4's were okay for originals, but the prevos sucked huge dinosaur balls and the evos weren't that great either. Gen.5 was a mixed bag like 2.
Gen.3 has the best balance/over-all design, IMO. Zigzagoon is a boss.
Official Naga Raja of the SMT IV board. Currently playing: Final Fantasy Tactics Advance
Their designs/bases were inspired (Claydol, Flygon, Metagross, Mawile, Tropius, etc.), but from a gameplay point of view they were mostly mediocre with a few exceptions at opposite ends of the list. They haven't improved much since.