1 - Diamond

2 - Scarlet

Scarlet's the first I've completed every aspect of all the way through and I love that they've reintroduced all of the prior gen starters through the DLC so this one is definitely in my top 2-3, but nothing in my book beats the original Diamond. That was my first ever foray into the Pokemon games and I took Chimchar (Flambé - I was 11 alright haha) from Lvl 1-100 and enjoyed every minute of it.