Gen 1: Jynx
Gen 2: Smoochum
Gen 3: Illumise
Gen 4: Rhyperior
Gen 5: Samurott (more disappointing than terrible)
Gen 6: Aromatisse/Slurpuff
Best Designs
Gen 1: Snorlax (Charizard is my favorite and my heart wants to pick it, but I think it's a pretty basic dragon, even if it's extremely well designed. Snorlax is a perfect example of what it meant to be a pokemon in gen 1. Idea: Fat huge lazy creature that looks cool still somehow. The execution is perfect. Honorable Mention: Charizard, Cloyster, Lapras, Alakazam, Gengar, Nidoking/queen)
Gen 2: Scizor (The archetype for Gen 4. Lots of evolutions of prior pokemon, all of them better than their predecessors. The babies, not quite as good, but eh. Scizor wins by looking like something in the wild, but slightly beyond and having a fairly flawless design. Honorable Mention: Heracross, Xatu, Ampharos, Donphan, Tyranitar, Houndoom, Kingdra, Legendary Beasts)
Gen 3: Metagross (Gen 3 has the largest amount of really strong designs, but Metagross was not a hard choice at all. It's the perfect pokemon. It looks powerful, interesting, yet alive and wild. Did it inspire humans or did we inspire it? Honorable Mention: Flygon, Sceptile, Swampert, Aggron, Torkoal, Gardevoir, Cradily, Salamence, Exploud, Breloom, Every Legendary)
Gen 4: Torterra (thought of giving it to Lucario since I think Torterra would be better if there was always variation in where the tree and cliffs were on its back, my autism isn't that bad so I didn't. Honorable Mention: Lucario, Cranidos, Empoleon, Abomasnow, Spiritomb, Croagunk, Dusknoir)
Gen 5: Reuniclus (Like Metagross, this one is a landslide. Fantastic design idea and execution. Am I just discovering that I should be a Psychic Type trainer? Honorable Mention: Archeops, Zeckrom, Volcarona, Golurk, Genesect)
Gen 6: Greninja (It's just barely beating Aegislash, for me. Honorable Mention: Aegislash, Both Box Legends, Zygarde, Malimar, Dragalge, Clawitzer)
Overall:
3>5>1>2>6
>>4