This is hard for me, I love the Pokemon series like it's a family member.
I ended up going with Gen 2. Being able to go between the first two regions was a plus, no doubt, but the variety of Pokemon was great too. All the new features being implemented and showing that there was more to Pokemon than the original just made it my favorite, after some hard thoughts. After Gen 2, Pokemon started losing it's touch, but it's still an enjoyable series and I'm glad to include it in my game collection.