They've all done their part
Atari - The first "successful" gaming console
Nintendo (NES) - 64 million sales brought gaming to the mainstream
PS1 - First successful CD based console. 100 million sales really expanded the market. And brought in a more "adult" market
PS2 - 125-140 million sales or so and counting. Its really expanded the market. Also its the first to be a "home entertainment system" since you can watch DVD's and listen to CD's.
Xbox - Although Sony had SOCOM, Halo 2 really made online gaming fun. Live is the best online network right now.
Wii - Expanding to a more casual audience. Very family friendly and still fun for young gamers.







