Ultima I
Ultima II
Ultima III
Ultima IV
Ultima V
Ultima VI
Ultima VII
Ultima VII - Part 2
Ultima VIII
Ultima IX
Ultima Underworld I
Ultima Underworld II
Worlds of Ultima I
Worlds of Ultima II
Runes of Virtue I
Runes of Virtue II
Ultima Online
Ultima I-VI Series - Origin Edition
Others: Software Toolworks Ed.

Other compilations

Ultima Collection Ultima IX + Ultima Online
Ultima Trilogy Underworld Series
The Second Trilogy Miscellaneous
The Complete Ultima VII  
Year of Release: 1993
Publisher: Origin Systems Inc.
Contents: Ultima Trilogy Manual, Age of Virtue, Reference Guide, Install Guide, 3 cardboard maps 1st Trilogy (18 x 12" / 45 x 30 cm), 1 cardboard map 2nd Trilogy (16 x 16" / 40 x 40 cm), 1x CD
Basically, the Ultima I-VI Series CDs are just the two previous trilogy releases combined into one. They contain all the maps and manuals, only the software is on CD instead separate disks.
It should be noted that as a side effect, Ultima II got broken and is missing vital parts from the original Galactic Disk. (this has not been corrected on any of the following CD compilations since).