In order, all of the main Pokemon RPG's are:

KANTO

Red
Blue
Yellow

Also:
FireRed
LeafGreen

JOHTO

Gold
Silver
Crystal

HOENN

Ruby
Sapphire
Emerald

SINNOH

Diamond
Pearl
Platinum

Spin-offs (games that aren't classified as the color/metal games) not in order

Pokemon Dash
Pokemon Trozei
Pokemon Ranger
Pokemon Mystery Dungeon (explorers of time, explorers of darkness)
Pokemon Mystery Dungeon (Red rescue team, blue rescue team)
Pokemon Ranger: Shadows of Almia
Pokemon Pinball: Ruby and Sapphire
Pokemon Puzzle Challenge
Pokemon Pinball
Pokemon TCG (Trading Card Game)


Non- hand held console games not in order

Pokemon Battle Revolution (PBR)

My Pokemon Ranch

Pokemon Puzzle League

Pokemon Snap

Pokemon Colosseum

Pokemon XD: Gale of Darkness

Pokemon Channel

Pokemon Stadium