What is your favorite Pokemon game?

I agree with @ShadowUmbreon
SoulSilver is my fave as there are so many things to do after you complete the game and there are two regions to explore. Also the pokewalker is a great little thing to have.

Has to be Platinum, hands down.

Although I do like many of the Pokemon games, I'd have to say my favorite is Pokemon Gold. I know that Heart Gold and Soul Silver have been released, but I feel that there is no way to beat the original. Also, Pokemon Gold was the first video game I ever received, so it's very special to me.

1. Heart Gold for the reason that you get 2 regions and they were both the original 2 so bring back memories :')
2. Emerald just because I frickin love it!
3. Black 2 because I love the storyline and the new features
4. Fire Red - Memories (even though heart gold includes it, in this you start in pallet town and get charmander etc)
5. Platinum is great, nothing really special but love the pokemon

sapphire, most nostalgic for me.
Even though I played them all in order.

A tie between Platinum and SoulSilver

HeartGold was perfect in every way, imo. I was upset when they threw away a lot of the mechanics that made it wonderful when Black and White rolled out. Such as the following pokemon, the permanent run button, the berry pods, perfect. That being said, Gen 3 was my favorite overall. I would looooove to see remakes some time soon.

Pokemon Heartgold and Soulsilver, 'nuff said.

I personally like Emerald the best. Sapphire was the first video game I ever played, and Emerald is prett much Sapphire that takes longer to beat. After that I played Red version, and Blue, then my mom bought me a DS and Pearl version, and I loved that almost as much as Gen III. I didn't play Gen II until HGSS, but it was good too. I personally didn't like Gen V very much, the Pokemon seemes a little...desperate.

probably these new ones? has a lot more features than the earlier games

For me has to be Black2, I have had so much fun on it, even if I'm already with the elite 4, I still feel like I"m only half way done, there are lots of other places I have yet to explore.

My favorite Pokemon game is Emerald. Fire Red is my second favorite. They are my favorite because Generation 3 was my introduction to Pokemon.

I still fondly reminisce over my Sapphire playthroughs. I did like Platinum too.

I really enjoyed Soul Silver. The graphics were nice, it was all updated with Gen 4 mechanics and such but was stiil nostalgic because of Johto. I had a great time playing and using Pokemon that I first started out with and I really liked the Pokemon following you.

In terms of all the pokemon games i would say Explorers of Sky is my favorite personally, but in the main series i would say emerald, as it cleanly combines ruby and sapphire's Team Magma and Team Aqua, and i love the music, the pokemon, everything in Emerald i pretty much love.