Dynasty Warriors: Gundam 3

By viewing the System > Gallery at the Main Menu screen you can check your progress and percentage inside the Movie Gallery, as well as re-watch the movies you have unlocked. There is a total of 24 movies and you can unlock the majority of these movies via story mode and history mode, but here is how I break it down:

Story Mission - 18, History Mission - 4, Special Mission - 1, Challenge Mission - 1, Total = 24 Movies

Here is a list of the movies and where they are unlocked. Note that the unlocks vary from person to person so the order in which they are obtained may be different. This list is in the sequence in which they are presented within the movie gallery:

Story Mission

A Time for Fighting
This is the opening cutscene upon first playing the game.
- Easy stuff as it unlocks just by playing the game for the first time.

Fateful Confrontation
Those Who Understand / Fated Showdown / Kou
Those Who Fight / The White Devils / Gato
- Playing either mission unlocks this movie.

The Reformers
Those Who Understand / Distorted World / Setsuna
Those Who Doubt / The Revolutionaries / Ribbons
- Playing either mission unlocks this movie.

Unicorn by Moonlight
Those Who Doubt / Beneath this Broad Sky... / Banagher
Those Who Pass By / Moonlit Unicorn / Garrod
- Playing either mission unlocks this movie.

Second Coming of the Red Comet
Those Who Fight / Return of the Red Comet / Frontal
Those Who Pass By / The Moon, Jupiter, and the Red Comet / Loran
- Playing either mission unlocks this movie.

Waypoint to Space
For Peace / Guides to Space / Player's Choice
- Simply clear this mission to unlock.

Storm from Hell
For Peace / Confrontation 1 / Doman
- Movie unlocks at the beginning of the mission.

Rise, Knight Gundam!
For Peace / The Knight Gundam! / Player's Choice
- Movie unlocks at the beginning of the mission.

End of Battle
For Peace / The Knight Gundam!
- Simply clear this mission to unlock.

End of Judgement
For Victory / The Knight Gundam!
- Simply clear this mission to unlock.

Duel, Knight Gundam!
For Victory / The Knight Gundam! / Player's Choice
- Movie unlocks at the beginning of the mission.

Vessel of Consensus
For Reform / Consensus of Opinion / Frontal
- Movie unlocks during the mission.

Overflowing Light of the Heart
For Reform / Light from the Heart / Banagher
- Movie unlocks during the mission.

Beyond Time
For Reform / Towards Time's Destination / Amuro
- Simply clear this mission to unlock.

A World in Motion
For Reform / Shake the World / Ribbons
- Movie unlocks at the beginning of the mission.

A Time for Reformation
For Reform / Reformation / Setsuna
- Simply clear this mission to unlock.

Fight, Knight Gundam!
For Reform / The Neverending Battle / Player's Choice
- Movie unlocks at the beginning of the mission.

An Endless Battle
For Reform / The Neverending Battle
- Simply clear this mission to unlock.

History Mission

Last Shooting
Mobile Suit Gundam
Escape / Amuro
Space Fortress A Baoa Qu / Char
- Playing either mission unlocks this movie.

Riders in the Sky
Mobile Suit Z Gundam
Riders in the Skies - Epilogue / Kamille
Riders in the Skies - Epilogue (Titans) / Scirocco
- Playing either mission unlocks this movie.

Warriors, Again...
Mobile Suit ZZ Gundam
Warriors, Again... / Judau
Warriors, Again... (Neo Zeon) / Haman
- Playing either mission unlocks this movie.

Space Rainbow
Mobile Suit Gundam: Char's Counterattack
Space Rainbow (Lando Bell) / Amuro
Space Rainbow (Neo Zeon) / Char
- Playing either mission unlocks this movie.

Special Mission

A Legendary Giant
The Giant of Legend / Knight Gundam
- This is somewhat of a multi-step process to unlock this movie and most likely may be the last one you'd unlock. First you need to unlock the Knight Gundam by finishing all of the Story Mode. A mission will unlock in the "Special Mission" section called "I am the Knight Gundam!", complete that with your preferred pilot and mobile suit and the Knight Gundam will be unlocked to develop a friendship with. You can keep replaying this mission (making sure Gundam Knight is an ally) to raise the friendship until you reach friendship level 3 and Gundam Knight is unlocked as a pilot.

There will also be a follow up mission called "Hero of Lacroix" unlocked for the Gundam Knight which in completing will unlock the next mission called "The Giant of Legend" which contains the movie needed to unlock once completed. Please note that you need to be well into level 4 friendship in order to play "The Giant of Legend" which also serves as his relationship mission to put Gundam Knight at level 5 friendship after completion. Grinding is pretty easy, just keep replaying "I am the Knight Gundam" with the Knight as an ally and "Hero of Lacroix" to play as the Knight, both methods help raise the friendship.

Complete "The Giant of Legend" to unlock "A Legendary Giant" movie in the gallery.
(credit to Setsuna x360a @xbox360achievements.org for this unlock info)

Challenge Mission

A True Dynasty Warrior Gundam!
My Master is the True Dynasty Warrior Gundam! / GM-1
- You do not have to complete this mission to unlock as it plays/unlocks during the opening of the mission. This unlocks when "Graduation Exam" is completed in the Tutorial Missions.