One of the greatest foes ever created in the Star Trek Universe. There were some great stories written with the Borg as the focal point, including the fantastic movie 'First Contact', unfortunately not in this collection.
DS9 has almost no appearances by the Borg except for the pilot episode 'Emissary' where the events from the TNG episode 'The Best of Both Worlds' are part of the brief back story of Benjamin Sisko's character. That episode is not included here.
The Next Generation: "Q Who"
The Next Generation: "The Best of Both Worlds"
The Next Generation: "The Best of Both Worlds, Part II"
The only episode from Enterprise is chronologically the first time the Borg appear on TV ('First Contact' being their first time chronologically overall), but not the first time we've seen them on-screen. It's a decent episode which ties in well with the Borg stories from the other series, but also raises the question of why they were never mentioned in the original series, which came after Enterprise chronologically.
The TNG episode 'Q Who?' is the Borg's first appearance on TV. It's the start of a beautiful friendship, sort of.
'The Best of Both Worlds' was hands down, the best Borg story written for TNG. The image of Picard is Locutus at the end of Part I is shocking the first time you see it. Good stuff.
The Next Generation: "I Borg"
The Next Generation: "Descent"
The Next Generation: "Descent, Part II"
'I Borg' and 'Descent' form a loose story arc. They are decent stories, but not quite the highest quality writing TNG has seen. Some of the concepts in these episodes, especially Data's desire to feel human emotions, is explored in much more detail and depth in 'First Contact'.
Voyager was the show with the most Borg appearances and not all of them are included in this collection, but the better ones fortunately have been. Of all the Star Trek TV series, the best Borg stories were from this show, and they tend to involve Seven of Nine a whole lot.
'Scorpion' sees the introduction of Seven's character and her escape from the Borg collective. 'Drone' is another high quality story, which has her as a supporting character central to the story. The best of the lot is 'Dark Frontier', which brings back the Borg Queen, a character that had a central role in 'First Contact' as well. The story explores the back story of Seven/Annika and the struggle between her lingering Borg identity and her human one.
It's almost fitting that the finale of Voyager ('Endgame') had a major part for the Borg, though I'm generally iffy on time travel stories personally. 'Unimatrix Zero' sees Captain Janeway do a Picard and have herself assimilated into the Borg. It's adds an interesting facet to the Borg mythos. While the story wears thin over two episodes, it's still a very good story.
This collection should be a blockbuster punch in the guts kind of collection, in theory anyway. The problem is that the selection is so varied that it's not possible for any narrative to build up, unlike the other themed collections.
(Disc 1) Star Trek
"The City on the Edge of Forever"
"The Enterprise Incident"
"Balance of Terror"
The first episode on this disc, 'The City on the Edge of Forever', is a classic, one of the best episodes in the original series. William Shatner's introduction is weird, incomprehensible in parts and I'm not convinced he knew what the episode's plot actually was.
The other two episodes revolve around the Romulans. 'The Enterprise Incident' is really good, though it's more of a Spock episode than a Kirk one and I'm not sure why it's included here. 'Balance of Power' is so-so, a straightforward combat story that doesn't leave much of an impression. Not one of my favourites, and that fact that it is popular enough to warrant inclusion baffles me.
(Disc 2) The Next Generation
"Chain of Command"
My favourite on this disc is 'In Theory' which is directed by Patrick Stewart and largely centres around Data. One of the better episodes in this series.
'Chain of Command' is one of those episodes that leaves an impression the first time around, but once the shock wears off, you realise that the story is relatively weak. Patrick Stewart gets a chance to flex his acting muscles, which makes it worthwhile to watch again.
'Darmok' is a very good episode based on the theme of trying to understand an incomprehensible alien language. It's a theme that's been used by Star Trek writers for pretty much every show in the universe and usually results in an interesting episode.
(Disc 3) Deep Space Nine
"Far Beyond the Stars"
"What You Leave Behind"
"In the Pale Moonlight"
Deep Space Nine is a hard beast to fathom. It's largely episodic, which makes it difficult pick out individual episodes of excellence. The whole disc, while not boring for a Trek fan, is pretty flat.
'Far Beyond the Stars' bucks the trend. It's basically social commentary on racism with a clever plot and steps outside of the DS9 continuity, making it easy to enjoy individually.
'What You Leave Behind' is the series finale and I'm confused at to why it's in this collection, since the Captain is one character is an ensemble cast.
'In the Pale Moonlight' is very focused on Sisko and deserves to be here but the story also makes little impact outside of the DS9's larger context.
(Disc 4) Voyager
"The Omega Directive"
Another reasonably solid set of episodes on this disc, 'Counterpoint' being the best of the lot. Voyager's penchant for building up the tension till the very end and finishing up with a relatively weak quasi-scientific plot construct has always bothered me. Both the other episodes suffer from this problem. They are still enjoyable, but not my favourites from the series.
(Disc 5) Enterprise
"These Are the Voyages..."
A very good set of episodes from Enterprise. I'm not sure how so many series finales ended up in this collection, but 'These Are the Voyages...' is another one. The good thing about Enterprise was always it's penchant for plugging into the history of the Trek universe created by the other series that preceded it.
All the episodes here follow that trend, and personally, I enjoy them all the more for that. The finale ends with the formation of the Federation, 'Judgement' digs into Klingon history and 'First Flight' is about the history of the Earth Starfleet. Interesting plots, all of them.
This disc is the only one that maintains some sort of narrative, that of the history of Starfleet / the Federation, and is more enjoyable for it.
Every Star Trek show has explored alternate realities that resulted in some of their best episodes. The original series started the trend and arguably has the best episodes in this collection. The image of Spock with a goatee in the mirror universe, a classic, and rightly on the cover of the DVD set. The Enterprise episodes featuring the mirror universe are also among the best material they produced.
Mirror Universe: (Disc 1)
Star Trek: "Mirror, Mirror"
Deep Space Nine: "Crossover"
Deep Space Nine: "Through the Looking Glass"
Deep Space Nine: "Shattered Mirror" (Disc 2)
Enterprise: "In a Mirror, Darkly"
Enterprise: "In a Mirror, Darkly, Part II"
Parallel Dimensions: (Disc 2)
Star Trek: "The Alternative Factor"
The Next Generation: "Parallels"
Twisted Realities: (Disc 3)
Star Trek: "The Enemy Within"
Star Trek: "Turnabout Intruder"
The Next Generation: "Frame of Mind"
The third disc contains episodes that aren't strictly different "realities". They feature individual characters that have somehow developed an alternate or 'evil' personality. Again, it's a trend started by the original series.
Fan Collectives are DVD sets that contain episodes from all Star Trek TV series (Star Trek, The Next Generation, Deep Space Nine, Voyager, Enterprise) that are related to a central theme.