pokemon omega ruby/alpha sapphire

X/Y

I enjoy basically all of them. But though these are Fan-Made, I like both Pokemon Uranium and Pokemon Phoenix Raising.

Pokemon Rubi and Pokemon Ultra Moon (About his Difficulty)

Pokemon Diamond/Pearl for the nostalgia and Heartgold for its quality. I also love Gold/Silver/Crystal (Virtual Console) and Alpha Shappire.

From the side games, Mystery Dungeon Explorers Of Darkness/Time are my favourite.

FRLG, Emerald, Platinum, HGSS, BW, B2W2, ORAS

I love all of them from gen 3-5. I grew up with leaf green though so I would have to pick that one as my favorite.

Pokemon Black 2.

I grew up with Red/Blue so it holds more closer to me, but I enjoyed Silver/Gold since you can play within 2 regions, collect 18 badges & such, but deep down, I really enjoyed Ruby/Sapphire a lot, so it's really hard to say. As for a spin-off, I'm actually really enjoying Legends a lot because I've always wanted to play pokemon in the old era.

hgss/oras

Pokemon Emerald

pokemon ultra sun/ultra moon

all pokemon games

Since the very first pokemon games on the gameboy (yellow/red/green/blue) i only played pokemon go and lets go pikachu. I like both. But for many reasons my fav ever is the first mentioned (pokemon go) due to the many functions and higher tempo that i enjoy. That said, i am a casual pokemon enjoyer therefore not very well known of the different games in the series. Also i will probably never play most of them as their tempo is too low for my tastes.

mines gotta be Pokemon HG/SS (100% nostalgia bias)