Not necessarily your favorite region/generation but what GAME is actually the best?
For example, Sinnoh is a pretty good region but Diamond and Pearl are HORRID games. Luckily, Platinum fixed most of its problems.
On the other hand, Unova is a pretty awful region. It's very linear, and the Pokemon are obvious Kanto ripoffs. Yet, it still manages to be an enjoyable game, mainly because of its storyline.
Pikachu following you wherever you go 