Gen 1: not much reason to vote here except for nostalgia
Gen 2: Arguably has the best legendaries, love the lore, beautiful region, arguably best rival and a very solid story
Gen 3: solid legendaries, love the lore, "meh" region, Battle Frontier, Steven Stone
Gen 4: Cynthia, amazing lore, amazingly beautiful region, some of my favorite Pokemon, really great story
Gen 5: amazing features, fun region to explore though not as beautiful imo, cool legendaries, average lore, in-depth characters, interesting story, Pokemon were hit and miss
Gen 6: (XY) Beautiful region, lots of promise, poorly executed, possibly my favorite region for new Pokemon, Mega evolution. (ORAS) Delta Episode, improved story, Steven Stone, still a lot of water, cool features
Gen 7: Tied with Sinnoh and Kalos for favorite Pokemon, slow story but good story, trainers challenge you to be Champion, hit and miss on character development but still my favorite batch of characters
In the end I voted Gen 2 but I could have easily voted for Gen 4 or 7