Hey, Quinn!
Welcome to PokéCommunity! How long have you been playing the series for? :D
I was also an avid card collector years ago, but I've stopped collecting for a few years now. If you've just returned from a large hiatus, we now have five generations of games released, and generation 6 will be making its debut this October with Pokémon X & Y for the 3DS!
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Here's a list of the main English handheld games released thus far so you know what has been released (I also included what console they are for):
Generation 1
Pokémon Red (GB)
Pokémon Blue (GB)
Pokémon Yellow (GB)
Generation 2
Pokémon Silver (GBC)
Pokémon Gold (GBC)
Pokémon Crystal (GBC)
Generation 3
Pokémon Ruby (GBA)
Pokémon Sapphire (GBA)
Pokémon Emerald (GBA)
Pokémon FireRed (remake of Red/Blue - GBA)
Pokémon LeafGreen (remake of Red/Blue - GBA)
Generation 4
Pokémon Diamond (DS)
Pokémon Pearl (DS)
Pokémon Platinum (DS)
Pokémon SoulSilver (remake of Silver/Gold - DS)
Pokémon HeartGold (remake of Silver/Gold - DS)
Generation 5
Pokémon Black (DS)
Pokémon White (DS)
Pokémon Black 2 (Sequel - DS)
Pokémon White 2 (Sequel - DS)
Generation 6
Pokémon X (to be released this October for the 3DS)
Pokémon Y (to be released this October for the 3DS)
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I do hope you stick around for X & Y, and you should definitely try the games you missed while away from the series! xD
Hope to see you around, and enjoy yourself!