There was a lot of ice cream in Brood War for the non-competitive gamer. And maybe this is more important than we realize.
I'm not sure what I would say regarding BW but that it was a very lucky game as were most games of the time in fact. For instance if you watch speed running competitions you'll see that there were apparently a million random elements in old games.
For the competitive scene there was obviously the advent of Mutalisk micro (which characterized all the zerg matchups, but especially ZvZ and ZvT). This is obvious the type of spontaneous event that is hard to comprehend.
But actually look how many spontaneous developments there were. Vultures jumping cliffs, Dark Templar pushed through walls, Boxer's CC interceptor stomping... Less flashy developments like Protoss FE walls and later Zerg expansion walls. Then more mundane things we take for granted like Dark Swarm Lurker burrows, Terran walls, Lurker drops (especially on cliffs), Arbiters (?), and so on.
From the run-of-the-mill perspective we attribute to the programmers, almost all of this was in some sense unprecedented or a priori.
To continue briefly about the competitive game, not only in the gameplay, but also in the map making. Maps like Valhalla, Jungle Story, Monte Hall, Forte, Requiem, Peaks of Baek Du, were all competitive maps with entrance into the competitive scene.
There were these maps and many more that created a very strange game dynamic. In later BW and the middle stages of SC2, the maps became homogenized to a greater degree. When we look at BW, a lot of people think Lost Temple, Luna, Python, and Fighting Spirit (which are pretty standard).
But in fact most of BW's history was characterized by truly bizarre maps. Championships were decided on maps like Valhalla; that weird map with the massive temple of ramps and island at 6; destination, and maps like that char-map (I forget what it is, but it had a mineral only semi-island)... Anyway the game's development was very spontaneous and even the professional scene had a lot of very "buggy" unreliable features.
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But maybe even more important than all this was the gaming environment for what we might term casual players. By casual I guess I mean non-professional.
There were a lot of ways to waste time. Most memorably for me, there was the Lord of the Rings game, MTG, a variety of RPGs, BGH and other money maps, map editing, playing with cheatcodes against computers, making maps (like Fighting Spirit), and so on. And maybe this more than anything calls to mind the glory days of BW (as a kid).
It is important to note how much more casual the gaming environment was. Today almost every game is quite stream-lined for competitive play as really only games like Halo and Counter-Strike were back in the late 90's and early turn of the millennium. Although I feel like I am somewhat out of touch with gaming today, there seems to be this feeling that FPS games like Halo, Call of Duty, and perhaps even Overwatch are the majority of the market, and on PC games like LoL, DotA 2, and HotS are also extremely competitive.
Maybe this is an ironic twist that we should associate StarCraft with Korean StarCraft when we really don't hold to that association. Actually most Brood War was pretty casual (but in a competitive dramatic way). There were a lot of grudge matches, a lot of drama, and a very interpersonal story arc.
It seems possible that in the making of StarCraft 2, the focus was on creating a game appropriate to the professional scene in South Korea. This makes sense at face value because in some way the professional scene was the brightly shining top of an iceberg.
But actually what supported the professional scene was the very rough-and-tumble team system, channel system, and "clan" system that ended up bridging so many games. StarCraft clans were pretty notorious for tackling a variety of games from counter strike to Diablo, poker and other experiences also. There were some prestigious clans, like ToT), Liquid, 88), [STiM], and others with rigorous testing procedures and internal drama.
Looking back on BW I think it was this kind of team system that created a lot of the energy for the game. Most teams had their own hack websites, their own channels with bots, their own celebrities and their own personalities.
There was also a lot of trouble areas that created interest like the annual WCG competitions wherein players of all calibers could participate for the chance to travel and play StarCraft. The game was more sustaining probably because it was intentionally personal. For instance a lot of players clamored for the opportunity to play a game or two with notorious personalities. There were a lot of gaming cabals, and the actual art of improvement at StarCraft was somehow political. This bizarre adolescent politic was probably one of the most formative elements in the culture of BW and may have sustained the game just as much as the quality of the game itself.