Gen 3. It felt like such a huge leap at the time going from gameboy color to the advanced plus we got the addition of abilities. The region felt very comfortable and I like pretty much every design.There being “too much water” was actually a plus for me since I love water Pokemon. I still miss diving to an extent since even though there were essentially just routes gated by an HM. Contests and Bases also were a great addition. Contests adding a different type of challenge to pursue was welcomed even though they were not the most difficult thing in the world. Bases really added that element of going off with your friend to make a fort in the woods and the fact you could have one of your friends bases that you could visit and challenge was fantastic (also a nice little xp/money boost each day)

It was fun to run through again in ORAS as well with the added benefits of including mega evolutions so Gen 6 is a close second for me partially for that reason.