In terms of best Gundam series, IMHO: Zeta Gundam, Victory Gundam, 0080, Turn A Gundam. Gundam X I have heard good things about, but it was cancelled at 39/49 episodes so the ending is most likely rushed.
SEED and Destiny both fall flat with re-used and poorly executed plot, poor character designs, and bland mecha designs.
Atlan:Mecha Anime Headquarters is a good site to read about all of the Gundam series.
Light's list is accurate in terms of in-story timeline, bit here it is in terms of releases:
Universe - Series Name - Year - Format - Available in US?
UC - Mobile Suit Gundam - 1979 - TV, 43 episodes - Yes
UC - Mobile Suit Gundam I - 1981 - Movie - Yes
UC - Mobile Suit Gundam II - 1981 - Movie - Yes
UC - Mobile Suit Gundam III - 1982 - Movie - Yes
UC - Mobile Suit Zeta Gundam - 1985 - TV, 50 episodes - Yes
UC - Mobile Suit Gundam ZZ - 1986 - TV, 47 episodes - No
UC - Gundam: Char's Counterattack - 1988 - Movie - Yes
UC - Gundam 0080: War in the Pocket - 1989 - OVA, 6 episodes - Yes
UC - Mobile Suit Gundam F91 - 1991 - Movie - Yes
UC - Gundam 0083: Stardust Memory - 1991 - OVA, 13 episodes - Yes
UC - Gundam 0083: Last Blitz of Zeon - 1992 - Movie - No
UC - Mobile Suit Victory Gundam - 1993 - TV, 51 episodes - No
FC - Mobile Fighter G Gundam - 1994 - TV, 49 episodes - Yes
AC - New Mobile Report Gundam Wing - 1995 - TV, 49 episodes - Yes
UC - Gundam: The 08th MS Team - 1996 - OVA, 12 episodes - Yes
AW - After War Gundam X - 1996 - TV, 39 episodes - No (cancelled)
AC - Gundam Wing: Endless Waltz - 1997 - OVA, 3 episodes - Yes
UC - 08th MS Team: Miller's Report - 1998 - Movie - Yes
AC - Gundam Wing: Endless Waltz - 1998 - Movie - Yes
CC - Turn A Gundam - 1999 - TV, 50 episodes - No
UC - G-Saviour - 2000 - Live Action - Yes
Various - Gundam Evolve - 2001->2007 - OVA, 14+ - No
UC - Green Divers - 2001 - Short Film - No
CC - Turn A Gundam I - 2002 - Movie - No
CC - Turn A Gundam II - 2002 - Movie - No
CE - Mobile Suit Gundam SEED - 2002 - TV, 50 episodes - Yes
CE - Gundam SEED Special Edition - 2004 - TV, 3 episodes - Yes
UC - MS IGLOO: The Hidden One Year War - 2004 - OVA, 3 episodes - No
CE - Gundam SEED DESTINY - 2004 - TV, 50 episodes - Yes
UC - Mobile Suit Zeta Gundam I - 2005 - Movie - Coming Soon
UC - Mobile Suit Zeta Gundam II - 2005 - Movie - Coming Soon
CE - SEED DESTINY FINAL PLUS - 2005 - TV, 1 episodes - No
UC - Mobile Suit Zeta Gundam III - 2006 - Movie - Coming Soon
UC - MS IGLOO: Apocalypse 0079 - 2006 - OVA, 3 episodes -No
CE - SEED DESTINY Special Edition - 2006 - TV, 4 episodes - No
CE - Gundam SEED C.E. 73 STARGAZER - 2006 - ONA, 3 episodes - No
CE - Untitled Gundam SEED movie - 200? - Movie - In Production
BlissGundam SEED: Astray is a manga series set in the SEED universe that began printing back in 2002. There are currently six minor series/sidestories under that name.
HEREGreen divers takes place at the end of Zeta Gundam.
Anime News Network wrote:Plot Summary: During the closing days of the Gryps conflict of Mobile Suit Zeta Gundam, two siblings — Asagi and Takuya — ride aboard a civilian transport bound for Earth. Caught in a battle between the Titans and AEUG, they must somehow guide their ship through atmospheric entry. Luckily, they're not completely alone, as they find aid from a custom-painted Zeta Gundam, whose pilot sounds a lot like One Year War ace Amuro Ray.