>BEST Battle Tower/Facility ever
>Fantastic Grand Underground, with Pokemon Hideaways
>No HMs
>Secret Bases that are actually useful for once
>Simplified Contests that are actually FUN to play, unlike in DPPt
>Ramanas Park
>Superior Gym Leader rematches
>Superior Pokemon League rematches
>Badass level 100 Shadow Giratina boss fight
>Postgame Dawn/Lucas battle
>Postgame Morimoto battles
>Superior Stickers Customization options, in both 2D and 3D
>Kept the Poffin making minigme, unlike what ORAS did with the berry Blending minigame
>Kept the Safari Zone game, unlike ORAS
>Trainer Customization
>Pokemon following you
>DS Sounds item
>All the QoL improvements from newer games like Mints, Bottle Caps, etc

I really like BDSP. It's the game that made me fall in love with Sinnoh, something that DP and Platinum couldn't achieve. The only thing I dislike about BDSP is the forced Amie bonuses. Otherwise the game is perfect imo.