Black 2 & White 2 Pokedex

It's a direct sequel set two years later, not an enhanced version. New protagonist, new rival, partially different gym leaders, and new areas like Humilau City and the Pokemon World Tournament. Old Pokemon are mixed into the regional dex from the start. The story continues from where BW left off.

Same three starters as BW. Oshawott is still the most flexible. But the starter matters less in B2W2 because you have access to a much wider pool of Pokemon early. You can catch an Riolu in Floccesy Ranch before the first gym.

A postgame facility in Driftveil City where you battle gym leaders and champions from every past region. Red, Blue, Lance, Steven, Cynthia, and every other major trainer appears. Each uses their signature teams. It's a fan-service gauntlet with real challenge.

Still Generation 5, released in 2012 for the Nintendo DS. B2W2 are the only numbered sequels in the main Pokemon series. They use the same engine and national dex as Black and White but tell a new story with expanded content.

Black 2 gets Reshiram and White 2 gets Zekrom (swapped from the originals). Black 2 has Black Tower (postgame trainer gauntlet), White 2 has White Treehollow (same concept, different layout). The non-legendary exclusives are minor. Pick based on which legendary you want.