Transformers series available on DVDA wide selection of episodes have now been released as complete season sets, although some series are still only available in part or in some countries.
THE TRANSFORMERS - also known as 'GENERATION ONE' / 'G1'
1984 - 1987
The series continued in Japan, substituting the Headmasters, Masterforce, Victory and Zone animated series for season four of the American cartoon.
Recommended resource: Rik Bakke's wonderful Cybertron Chronicle.
1992 - 1995
Just earlier American episodes edited to include CGI scene changes.
BEAST WARS and BEAST MACHINES
1996 - 2000
ROBOTS IN DISGUISE
2001 - 2002
ARMADA, ENERGON and CYBERTRON
2002 - 2006
2008 - 2009
Recommended resource: TransformersAnimated.com
2010 - now
Pioneer Cover Gallery
Beast Wars Profiles
Beast Wars 2 Profiles
Beast Wars Neo
Beast Wars Metals
Beast Wars Returns
Recommended resources: check out this forum thread for a selection of useful links.
Japan has seen a lot of extra Transformers stuff compared to the Western market.