I think that as I grew up, my favorite medium of Pokemon kept changing. When I first got into the franchise, it was because of the anime. I didn't even realize that the games were a thing, but I would never miss an episode of Pokemon when it was on. Then, when the TCG came out, I got hooked on that, even more so than the show.
Those two remained my favorite two mediums of Pokemon for almost 3 years, until I finally got a hold of Pokemon Yellow. From that point on I was hooked, and the games (the main series ones, at least), have remained my favorite part of the franchise.
I was first introduced to pokémon via the TCG ^^ And then the anime. I always knew there were games though, I just didn't play them until I became a young teenager, pretty much. Yellow and Ruby <3
I joined PC to get to talk manga with people though! I'd still say I love the pokémon world from the Pokémon Special/Adventures manga the most. So manga and the main games are probably my favorite medias.
The Pokémon games is the canon I like the best. The other canons don't really interest me as much; the anime is a bore for me (sorry Pokémon anime fans :x) and the manga is, well, let's just say that I just don't really like manga. So, yeah, I guess my favourite Pokémon medium is the games.
Games, definitely. Though my first encounter with Pokemon was with the original anime, we were all watching it as kids and collecting these stickers that came in 7days croissants. No one I know has ever played the games, and I actually started playing really late, only a year ago, because I was sure I'd end up loving it too much
I don't really watch the anime anymore, and I've recently started reading Pokemon Adventures. From the two, I like the manga more, though I may be a little biased, since I've only read the Ruby & Sapphire and Black & White sagas, corresponding to the games I've actually played.