I tried to make this review as long as I could and to detail as much as possible without spoilers, but there is nothing to say about it the product is really empty, even if you want to start overthinking / overacting, compared to some episodes.
I'm not interested in this kind of stuff and it's what die-hard fans usually do when they're too fanatical about something, and it's only to fill a gap in their favorite work, and it irritates a person who isn't necessarily a fan of the show and even fans, and it just doesn't make you want to watch.
Story: These are several separate episodes/compilations/short films gathering the most Gundam series, which was released so far, it's purely for the die hard fans.
And they don't tell anything relevant/interesting except to be entertaining I guess?
It tells a number of side stories, alternate scenes, that are obviously canon in the lore.
Art: It varies quite a bit, but it's very very often CGI mixed with average PlayStation 2 game graphics, it's pretty experimental and ugly for the date it was released.
Even if it would have been drawing and 2d, it wouldn't change anything to this disaster anyway.
Music: Nothing to remember about it, it's empty, it's a background soundtrack that you can hear anywhere.
You hear much more the sounds of the mecha weapons, than music or any semblance of background music.
Characters: Nothing to say about them, this anime/compilation doesn't bring them anything really important, except seeing them again in action for a banal secondary story.
And it's way too short to really judge the characters or even impossible in this compilation/short movie.
They appear just to make hardcore fans smile and because Gundam loves fan service and never stopped.
Enjoyment : Well I didn't get any, there is nothing interesting in this OVA, even for the biggest fans, it's a meaningless thing and not worth the time to invest in it, unless you want to consume all the content related to Gundam or always want more.
Overall: it doesn't bring anything interesting and it's a waste of time, it's too rushed and the execution is bad, I didn't really understand the point of this ova, even for die hard fans in need of content, I doubt they'll appreciate this thing.
I'm going to summarize the episodes below, without spoilers as much as possible, anyway there's nothing to say about it it's just empty and uninteresting for a lot of reasons, so if you're going to watch this ova anyway, free to choose to read or not, but nothing relevant will be stated, I just made synopsis/summary of the episodes.
Episode 1 = Amuro highlights, with the original Gundam, and a concentrate of 0079 action scenes, all in 6 minutes of episode, it's just a kind of Higlight/AMV.
Episode 2 = Zeta, a kind of augmented reality training/simulation for Kamille Bidan, to adapt/train, it's just a kind of report, and the animation is just similar to an average PlayStation 2/CGI game.
Episode 3 = Mobile Fighter G Gundam is a kind of advertisement, made with average PlayStation 2/CGI game graphics, it brings absolutely nothing.
Episode 4 = Mobile Suit Gundam Stardust Memory, a kind of entertaining action cutscene from a PlayStation 2 game.
Episode 5 = Mobile Suit Gundam: Char's Counterattack, a discussion between two characters who will be confronted because of fate and because they are two newtypes.
Episode 6 = FanService, it doesn't tell anything and it's not interesting, at the limit it can be entertaining, but it would be a lie.
Episode 7 = It's about the protagonist of Gundam Wing, I assume it's about his past/origin, I guess it's already been explained/displayed in the anime and its 8 minutes don't bring anything but an umpteenth CGI animation without much interest.
Episode 8 = Gundam Seed (if I'm not mistaken) again some action-entertainment and nothing more in CGI.
Episode 9 = Zeta, if I'm not mistaken and it's a weird episode too rushed and not enough built, it lasts 14 minutes to finally tell nothing.
Episode 10 = ZZ and it's still uninteresting, it's a kind of filler again, another pretext for fan service action.
Episode 11 = 0079, 9 days after the battle of Al A Bao Q, and it just shows the consequences of the war in a terribly badly executed way for no change.
Episode 12 = Zeta, focused on the character of Quatro Vagina and it's a pity it's too short, it's not a crazy episode but it's the best of all and it was watchable compared to the other purges.
Episode 13 = Zeta, and it shows the repercussions of conflict/war, again terribly executed.
Episode 14 = SD Gundam Sangokuden Brave Battle Warriors, little Gundams in a feudal samurai Japan era, it's not to be taken seriously and it's meant for children.
Episode 15 = 0079, it adds events that we don't know to some characters, but they are minor and absolutely not important and whether it is canon or not, has no real importance/impact.