Aside from the Main series, there has been many, Pokémon games. Any Generation has at least one spin off Pokémon game. These games try to go for a different theme. Whether it would be changing only the story or plot or introducing a whole new mechanic.
Some of these games come out as great, others are mediocre or just flat out terrible.
So what's your opinion?
Which Pokémon spin off game do you like the best? Which one was the worst?
Any game from any generation that isn't part of the main series games (E.G. Pokémon Battle Revolution, Mystery Dungeon, PokéPark, etc) and why you like or hate them.
I personally am a fan of Pokémon Puzzle League. It's fun and engaging (in not enraging on harder difficulties)
Now it's your turn.

My favorite spin off would have to be gale of darkness, I just loved the graphics and the story.

In my opinion, Pokemon Snap is definitely my favorite spinoff, and it warrants a sequel. It helped to give personality to the pokemon that it showed, and it also helped to illustrate  the pokedex entries, making it very interesting to observe pokemon in their natural habitat. I would absolutely love to see a new entry on the Wii U. It would work perfectly, one could use the game pad as a camera and have it move one to one. The new graphics and the many new pokedex entries would make the whole thing so much more interesting and cool. It would be great.

I'd say that the Pokémon Mystery Dungeon series are the best spin off series.  The battle system is more like a dungeon crawler than anything but I happen to like the battle style. It's more like my cup of tea than the main series. The story is very deep and sad in the middle and later half of the games. The basis is that you have turned into a Pokémon and you must find out why. In Red and Blue you go rescue Pokémon with a partner and in Time/Darkness/Sky, you are an exploration team that explores places. I don't know about the third game since I've never played it. It doesn't sound very deep, but if I were to expand more, I would spoil the story. Please play it for yourself if you want to see the whole story. Anyways, it's a great game series and I recommend it 100%.
 
My least favorite would have to be Pokémon Pinball. Sorry, I just never got into pinball. Pinball just bores me, to be honest.

I do have to say that my most of Pokemon spin-off game in the series has got to be the Mystery Dungeon series, because why I say that this is the best, I have Gateway to Infinity, and you play as a Pokemon and you go through a whole new adventure without any trainer interaction

Sam24 : My favorite spinoff game in the Pokemon series is the entire Pokemon Mystery Dungeon series except Gates to Infinity. The other mystery dungeons have the best storylines in the whole series and unlike the main pokemon series the Mystery dungeon series is pretty tough at times.

Sam24 : My favorite Pokemon spin-off game is PokePark and its sequel. Amazing story, gameplay, and graphics. You control Pikachu, U travel around PokePark to collect 14 Prism Pieces. You make many friends on your way, which fills your Friend Book whatever it's called. Many fun minigames. PokePark isn't bad for a spin-off game!!