Thinking of the next generation, I decided to do a little Wikipedia research. Yeah, the information is from Wikipedia and everyone has a wide ranging opinion of it's veracity, so take it with a grain or few of salt. Release dates listed in are from when they are first released, not by country unless it was only available in one country. If you want to argue "units sold," then please direct no ire at me as I am only going off of what is on each wiki page.  Here we go:

First Generation

Magnavox Odyssey 2000

Retail Availability: 1972

Discontinued: 1975

Units Sold: 330,000

http://en.wikipedia.org/wiki/Magnavox_Odyssey

Magnavox/Phillips Odyssey 100-2100 Series

Retail Availability: 1975 (100) - 1978 (2100)

Discontinued: ?

Units Sold: ?

http://en.wikipedia.org/wiki/Odyssey_200

Pong Home Version

Retail Availability: 1975

Discontinued: ?

Units Sold: 35,000

http://en.wikipedia.org/wiki/Pong

Coleco Telstar

Retail Availability: 1976

Discontinued: 1982

Units Sold: ?

http://en.wikipedia.org/wiki/Coleco_Telstar

Nintendo Color TV Game

Retail Availiabilty: 1977 (Japan only)

Discontinued: 1979

Units Sold: ?

http://en.wikipedia.org/wiki/Color_TV_Game

Second Generation

Fairchild Channel F

Retail Availability: 1976

Discontinued:  around 1979

Units Sold: ?

http://en.wikipedia.org/wiki/Fairchild_Channel_F

Atari 2600

Retail Availability: 1977

Discontinued: 1992

Units Sold: 30 million

http://en.wikipedia.org/wiki/Atari_2600

Bally Astrocade

Retail Availability: 1977

Discontinued: 1985

Units Sold: ?

http://en.wikipedia.org/wiki/Bally_Astrocade

Intellivision

Retail Availability: 1979

Discontinued: 1991

Units Sold: 3 million

http://en.wikipedia.org/wiki/Intellivision

Atari 5200

Retail Availability: 1982

Discontinued: 1984

Units Sold: 1 million

http://en.wikipedia.org/wiki/Atari_5200

Vectrex

Retail Availability: 1982

Discontinued: 1984

Units Sold: ?

http://en.wikipedia.org/wiki/Vectrex

Emerson Arcadia 2001

Retail Availability: 1982

Discontinued: ?

Units Sold: ?

http://en.wikipedia.org/wiki/Arcadia_2001

ColecoVision

Retail Availability: 1982

Discontinued: 1984

Units Sold: 2 million

http://en.wikipedia.org/wiki/ColecoVision

Sega SG-1000

Retail Availability: 1983

Discontinued: ?

Units Sold: ?

http://en.wikipedia.org/wiki/SG-1000

Third Generation

Nintendo Entertainment System

Retail Availability: 1983

Discontinued: 1995 (US) - 2003 (JP)

Units Sold:61.91 million

http://en.wikipedia.org/wiki/Nintendo_Entertainment_System

Casio PV-1000

Retail Availability: 1983

Discontinued: In a matter of weeks

Units Sold: ?

http://en.wikipedia.org/wiki/PV-1000

Epoch Cassette Vision

Retail Availability: 1981

Discontinued: 1984

Units Sold: ?

http://en.wikipedia.org/wiki/Epoch_Cassette_Vision

Sega Master System

Retail Availability: 1985

Discontinued: 1998

Units Sold: 13 milion

http://en.wikipedia.org/wiki/Sega_Master_System

Atari 7800

Retail Availability: 1984

Discontinued: 1987

Units Sold: ?

http://en.wikipedia.org/wiki/Atari_7800

Fourth Generation

TurboGrafx-16

Retail Availability: 1987

Discontinued: 1995

Units Sold: 10 million

http://en.wikipedia.org/wiki/TurboGrafx-16

Sega Genesis

Retail Availability: 1988

Discontinued: 1997

Units Sold: Disputed. 20-29 million.

http://en.wikipedia.org/wiki/Mega_Drive

Neo Geo

Retail Availability: 1990

Discontinued: ?

Units Sold: ?

http://en.wikipedia.org/wiki/Neo_Geo_(console)

Super Nintendo Entertainment System

Retail Availability: 1990

Discontinued: 2003

Units Sold: 49.10 million

http://en.wikipedia.org/wiki/Super_Nintendo_Entertainment_System

Fifth Generation

3DO Interactive Multiplayer

Retail Availability: 1993

Discontinued: 1996

Units Sold: 2 million

http://en.wikipedia.org/wiki/3DO_Interactive_Multiplayer

Atari Jaguar

Retail Availability: 1993

Discontinued: 1996

Units Sold: 250,000

http://en.wikipedia.org/wiki/Atari_Jaguar

Amiga CD32

Retail Availability: 1993

Discontinued: 1994

Units Sold: 100,000

http://en.wikipedia.org/wiki/Amiga_CD32

Sega Saturn

Retail Availability: 1994

Discontinued: 2000

Units Sold: 9.5 million

http://en.wikipedia.org/wiki/Sega_Saturn

Playstation

Retail Availability: 1994

Discontinued: 2000

Units Sold: 102 million

http://en.wikipedia.org/wiki/PlayStation_(console)

Nintendo 64

Retail Availability: 1996

Discontinued: 2002

Units Sold: 32.9 million

Sixth Generation

Dreamcast

Retail Availability: 1998

Discontinued: 2001

Units Sold: 10.6 million

http://en.wikipedia.org/wiki/Dreamcast

Playstation 2

Retail Availability: 2000

Discontinued: ?

Units Sold: 146.9 million

http://en.wikipedia.org/wiki/PlayStation_2

Gamecube

Retail Availability: 2001

Discontinued: 2007

Units Sold: 21.74 million

Xbox

Retail Availability: 2001

Discontinued: 2006

Units Sold: 24 million

http://en.wikipedia.org/wiki/Xbox

Seventh Generation

Xbox 360

Retail Availability: 2005

Discontinued: ?

Units Sold: 44.6 million as of September 30, 2010

http://en.wikipedia.org/wiki/Xbox_360

Playstation 3

Retail Availability: 2006

Discontinued: ?

Units Sold: 41.6 million as of September 30, 2010

http://en.wikipedia.org/wiki/PlayStation_3

Wii

Retail Availability: 2006

Discontinued: ?

Units Sold: 75.9 million as of September 30, 2010

http://en.wikipedia.org/wiki/Wii

Thank you for reading :)

Here are my own personal observations:

1. Video games are an American invention popularized and mainstreamed by Nintendo. Ralph Baer with the Magnavox Odyssey created the first home video game console. Prior, Thomas T. Goldsmith Jr. and Estle Ray Mann created the first patent on video games in December 14, 1948 with U.S. Patent 2455992. (http://en.wikipedia.org/wiki/Video_game#History).

2. Nintendo was founded September 23, 1889 by Fusajiro Yamauchi producing handmade hanafuda cards. Nintendo is the majority owner of the Seattle Mariners. (http://en.wikipedia.org/wiki/Nintendo).

3. Sony with Playstation and Playstation 2 has sold more units on 2 consoles than Nintendo sold entirely between the NES and Gamecube. 248.9 million  = Playstation and Playstation 2 vs. 165.65 million = NES, SNES, N64 and Gamecube. Absolutely fascinating.

4. With each successive generation from the 1st through the 6th, there has been less competition. Meaning, the industry has matured to a point where entry to the market is nigh impossible unless the new entrant has financial backing in the hundreds of millions of dollars.

5. There is no way to tell who will be the leader in the next generation by looking at the current generation or previous generations only looking at the "units sold."

interesting 

whats interesting that SONY has sold almost 50% of all video game consoles ever sold 

I've been lucky enough to play everyone of those consoles!

I went to a video games sorta... remembrance type day I guess where they had like.. every retro console in existence, and I managed to play the vast majority of them. The vectrex is frikkin ace!

It should be worth noting that SONY actually kept selling PS1's until 2005 or 2006 when stopped manufacturing them / stopped supporting the platform.  Other than that impressive list 

Epoch Cassette Vision is the most lame name of the list.

Jesus <_<

Nintendo kept producing new NES units in Japan until 2003, well into the Gamecube era, and stopped repairing NES units in 2007. New NES units were produced for a 20 year span in Japan and a 15 year span in the US. The only other console to live that long was the Atari 2600 which ran a UK Christmas television ad in 1989 after starting it's run in 1977.

Neo Geo and Dreamcast are my favorite console names on the list. I like the rhyme in Neo Geo and Dreamcast is perfect because it can be interpreted in so many different ways, which Sega may not have intended when naming it.

I would say Atari mainstreamed console games with the 2nd generation in America. The difference is that it came out in a still very immature market.

Wow i didnt know that Xbox was selling at 24millino before it discontinued and X360 got pushed out.. what a rush.. no wonder.. PS3 is closing the gap besides the fact that it launched a year later..