Two big trends in game design these days are "cinematic" game design (ala Uncharted 2), and "sandbox" games (ala Grand Theft Auto). These are trendy things to talk about, and tons of people have really strong opinions about one or the other type of game for various reasons. However, I think that both cinematic and sandbox games are the latest incarnations of a much broader division in game design that goes back to the roots of the industry or before.
As the title of this post suggests, I'm calling them Curatorial and Exploratory, and I think that all games can be lumped into being one or the other -- or, really, varying mixes of both. It's rare that anything would be one or the other only.
Curatorial Game Design
Curatorial game design has something to show you. It wants you to follow a certain set of rules, and it will take you through a progression. There may be some little deviations here and there from the main progression, but overall it's just a matter of how well you perform during the progression that determines the outcome. It's a linear test of some sort of skill, be that reflexes or mental acuity.
Examples of very curatorial games:
The Original Super Mario Bros, which has a linear progression of levels (warp zones aside, but even that is just branching linearity, there's no variance in them.
Half Life 2, which funnels the player through a heavily (and wonderfully) scripted world. Their trick is that they make the game seem more exploratory than it really is by having a few little nooks and crannies, but really it's a very linear progression nonetheless. It feels way less linear than other classics like Quake 2 because of its innovative level design.
Peggle, which primarily consists of a long string of levels that you move through completely linearly. There seems also to be some sort of Quick Play mode, but the menu organization makes it pretty clear that this is hugely secondary.
Pac Man (and most other classic Arcade games) is simply a long series of levels like Peggle.
Exploratory Game Design
Exploratory game design tends to throw the player into some situation, or a series of situations, and let them figure out what to do. This broad description manifests itself in all sorts of ways, but basically the key factor is this: the player is very frequently able to choose what their next challenge is.
Players have overall goals, and numerous other smaller goals that they can pursue, and they choose what they want to do. Ultimately if they want to win the game they probably have a set curatorial-style progression that they have to follow, but there is so much other content that the curatorial parts are just one facet of the wider exploratory design.
Examples of very exploratory games:
Grand Theft Auto and all the other sandbox games are, of course by definition, very exploratory. There is a set of central story missions, and then a bunch of other side missions, and then a whole wide world to explore and simply play around in. Personally I loved the first two GTA games back in the day but never played the story missions -- I was able to exist in that world simply by exploring around and dodging the cops and so forth, and never felt compelled to do much with the curatorial parts. I believe I used cheats to get to the second and third cities, because I wanted to go to them but had no interest in the story progression that would lead me there.
The original Legend of Zelda is a great example of a highly exploratory game. Later Zelda titles emphasize the curatorial a bit more, but still have a highly exploratory element. The original game allowed players to complete the dungeons in somewhat variant order, and the players could get all over the overworld pretty much from the start. Even just finding the next dungeon was a game in itself, and going about that was left up to the searching strategy of the individual player.
My own game AI War: Fleet Command is hugely exploratory. A very few players have complained that there was not a scripted curatorial-style campaign, but that's rather missing the point. AI War is built as the strategy-game incarnation of how I played GTA: there is stuff all around the galaxy for you to find, and there are goals big and small for you to pursue, and ultimately you have a goal but you can go about achieving that goal (and preparing yourself for that goal) in absolutely any way you want. Various other strategy games, mostly in the 4X side of things, emphasize the same: Civilization IV is another great example.
A Wide Spectrum
As I noted in the introduction, most games don't fall solely into just one category. Exceptions might be games like Sim City on the exploratory side (there's not even an overall goal, no curatorial content whatsoever) or the rail shooter subgenre on the curatorial side (there's absolutely no way to explore).
But everything else falls somewhere in between, and figuring out the balance between the curatorial and exploratory aspects is a real challenge. Clearly there are players who are very much fans of both. Personally I found that I couldn't get all that much into curatorial game Uncharted 2, while I developed a completely unexpected attachment to exploratory game Red Faction: Guerrilla. But by the same token I absolutely loved curatorial Half Life 2 (like seemingly everyone else), while having a hard time finding much interest in GTA III and beyond despite their exploratory aspects.
So clearly there is much more going on with all these games than just their curatorial versus exploratory aspects -- the actual execution of a game, plus all its interlocking mechanics, are what make a game appeal to certain players or not. And I definitely don't think that one method of game design is more "correct" than the other. I probably have some exploratory leanings, but not as much as you might expect from someone who made a game like AI War.
My big challenge back in 2008 with Arcen's upcoming Alden Ridge came from me struggling with integrating exploratory aspects into a game that had started out completely curatorial. Our current game-in-beta, Tidalis, is a pretty much even blend of curatorial and exploratory, in that it has a linear adventure mode, but that's only a small portion of the wider game modes and options that are available (and even in the adventure, there are secret levels everywhere -- almost as many of those as regular levels in the main progression).
If you look at a lot of successful contemporary games, like the Mario Galaxy games for instance (or any of the 3D Mario games, really), they have a huge mix of curatorial and exploratory design elements. There is a linear progression of levels, sort of, but each level has multiple goals in it, and many of those are optional and/or can be done out of order. You can "beat the game" by simply collecting 70ish stars/shines out of the 120 that tend to be present, and you can do so in any order you want. Demon's Souls is another game like that: it starts out linear, and the individual levels are all pretty linear, but there are a lot of side branches that are optional, and the order in which you approach the levels is something you can switch up to a fair degree. More so than the recent Zelda games, and more on par with the original Zelda, at least.
All this buzz exists around cinematic games and sandbox games, but the underlying principles at work here are as old as the medium.
The more curatorial games often create experiences that are more resonant in a storytelling sense because of the increased control they give designers; and when you pair that with the "cinematic" techniques of games like Uncharted 2, the result is definitely something Hollywood-esque. There are some seriously great things about that approach, but you also lose a lot of what makes for replay value in games, and a lot of player agency is lost as well.
On the exploratory side, there is a ton of player agency, but it is a really fine line to walk to not have players just feeling like nothing really matters and that the world is boring to inhabit. That was my challenge with the later GTA games, so clearly that's something that varies by player taste -- others were really compelled by those games in a way I was not. It's also pretty hard for players to feel emotionally invested in a purely-exploratory game if it doesn't have at least a single thread of curatorial progression. I think that's where the occasional complaint of the lack of scripted story in AI War comes from. It's also why players aren't emotionally attached to Sim City in the same way that they are to, say, Chrono Trigger (my favorite game of all time, alongside Final Fantasy VI, for the record).
I think it's telling that the games that I consider to be my overall favorites, and which I had the greatest emotional response to, where all mostly-curatorial with some exploratory sections: Chrono Trigger, FF6, and Silent Hill 2. But at the same time, the recent games that I most enjoy playing, and that I think back on with the fondest memories of inhabiting, are games that have large exploratory components: Red Faction: Guerrilla, Mario Galaxy 1 and 2, Far Cry 2.
To me, the debate over the merits of sandbox versus cinematic games could not be more pointless: it's like debating action versus comedy movies. Put simply, people should make more of all of the above!