I love Dialga. His cry is ADORABLE. He’s a dragon that can control time itself, but he makes a squealing sound. This is most noticeable when being petted (Gen 6 & 7) or romping around with other Pokémon (Gen 8 Pokémon Camp). Also, Dialga’s shiny is turquoise, which is the greatest color on the planet.
Dialga (I had a hard time choosing between the 3. All of them are nearly equally cool, but Dialga, the Time Dragon had to win for me.) > Giratina (Distortion World A.K.A. Let's-Flex-What-A-Nintendo-DS-Can-Do World was really fun! Also, Ghost-Type is my favorite type!) > Palkia > (The space dragon lost here, but I still love it! )
I love all three equally, especially their designs and type combinations. I ended up choosing Giratina as I mostly played Platinum more than the other two games, for obvious reasons relating to improved features. I also love Ghost-types, and the Origin Forme is badass.
Giratina because it's just much cooler and more interesting than the other two and also has two forms and its own world/reality. Dialga and Palkia are nice but they can't compete with Giratina in my opinion.
Giratina because of how mysterious it was in the games. It has a really cool design and its Origin Form is one of the best looking alternate forms in the games. Shadow Force is also one of the best moves in the series
Giratina. When you're essentially a rogue pokemon considered so dangerous that Arceus had to banish it into a special world (instead of removing Giratina from existence) then it truly is a interesting backstory.
Honestly can’t decide. Dialga will always have a place in my heart as my first Legendary since Diamond was my first game. Palkia’s design is probably my favorite and Pokémon Masters has made it even cooler. Also like its cry and signature move the most. Giratina is super cool as well with its 2 forms and backstory. I’d probably say Palkia but all 3 are pretty much equal