DLC in its current formulation is usually best implemented with larger, more open-ended games that have still told a complete story. The best expression of this idea of DLC is Grand Theft Auto IV's Xbox 360 release: Niko Belic's story is complete, but there's still this feeling at the end that Rockstar has left so much to explore in Liberty City. Hence The Lost and the Dammed expansion, which puts you in control of a relatively minor character introduced in the main game's story. It's an entirely new story with a new character, one that adds a bunch of hours to the game's lifespan and gives you a new voice and perspective on Liberty City. Rockstar has, in other words, added on to a game's world while managing to ensure that the core game was a complete experience.
In my mind DLC's modern roots lie with Valve Software. Valve's first Half-Life was a landmark moment in gaming and is the largest-selling first-person shooter of all time according to the Guinness Book of World Records. Yet there was a frustrating five-year gap between Half-Life and its sequel, with hordes of rabid fans practically beating down Valve's doors each time the game was delayed. Attempting to reduce the lag between fixes of the Half-Life drug, Valve announced that Half-Life 2 would receive periodic episodic content updates that continue the story, with the difference akin to that of weekly half-hour TV episodes and blockbuster film sequels every other year. There were a grand total of three episodes released through the company's Steam service -- which lets you download digital copies of a wide variety of games, as well as acting as an online matchmaking service -- and Valve co-founder Gabe Newell has said repeatedly that these three episodes in fact comprise Half-Life 3.
And although Half-Life 2 may not be the earliest roots of DLC, it's quite probable that the game's contemporaries are more significant. Half-Life 2 was a decent implementation of DLC insofar as all Valve did was develop a third Half-Life game and cut it into thirds, then release each part on Steam. Without the need to develop a new engine (as was the case for Half-Life 2), Valve's development time for the expansion episodes was cut down drastically.
Ritual Entertainment took a similar approach with its 2006 sequel to the 1998 game SiN. The game was intended to be released as a series of episodes -- titled, inventively, SiN Episodes -- and was the first game developed by a major publisher that was intended to be both released entirely episodically and sold online (via Steam, though at least the first episode was released on hard copy). However, only the first two episodes were produced, as Ritual was sold to MumboJumbo and all development on future episodes has ceased. This really isn't that much of a loss: while I enjoyed the first installment of SiN Episodes, I never really got the sense that I was playing something that really gelled as an episodic release. Indeed, SiN Episodes can really be chalked up as a failure for DLC, since the lack of continuing releases means that the game just stops on a cliffhanger. And I hate midseason cancellations that don't let writers at least attempt to wrap up plot lines.
Then there's Sam and Max Save the World, another episodic game released via Steam in 2006-7. This is, among the three early attempts at DLC stories (at least on PC), by far the best execution. There were a fair number of episodes, a whole story got told, and the development time was faster than on Half-Life 2 and SiN's episodes. Furthermore, what I played of the games left me with the distinct impression that I was actually following interactive episodes, rather than just periodic installments of a larger experience -- i.e., actually watching TV episodes as they air instead of watching a few scenes of a movie at a time.
But Half-Life 2's episodes, SiN Episodes and Sam and Max Save the World aren't really DLC: or rather, they represent a conception of DLC that seems to have been largely erased, but for a few notable exceptions that are almost entirely confined to PC and Wii. Fundamentally, they aren't additions to full games, but are instead portions of a full game. And as I've said, DLC is now seen as the former, not the latter -- or at least are seen that way by Microsoft and Sony, who are the two most visible distributors of DLC for games. Interestingly, the Wii's Virtual Console operates much like Microsoft's Xbox LIVE Marketplace and Sony's PlayStation Network insofar as all three publish full games -- generally priced around $10 -- that you can download to your console's hard-drive and play as you please.
However, the Wii tends to focus much more on having a wide variety of games from past consoles than the other two major consoles. There are a lot of different reasons for why this might be (such as liscensing), but there are two good reasons that fit particularly well with Nintendo's objectives for the Wii. First, retro(ish) games of the NES and SNES eras cash in on the nostalgia of the first generation of people who grew up playing video games, especially those who never did so in any hardcore manner: i.e. a significant chunk of the much-coveted, but massively-overhyped "casual gamer" market that Nintendo is courting so heavily with the Wii. These people are in their 20s and 30s, have disposable income, and want to play things that are easy to pick up and are a lot of fun -- the typical stereotype of games prior to the PlayStation era. (It's also worth noting that the Virtual Console games have an auto-resume feature, so even if you turn the console off you can come right back to where you were in a game whenever you feel like it). Of course, the reality is much more complicated than this (I could write a whole series on casual gamers alone), but as a thumbnail sketch that'll do nicely. Second, the Wii has little online play to speak of, instead emphasizing local co-op, whereas Microsoft and Sony are the exact opposite. Console games from before the current generation were almost entirely about local multiplayer or an exclusively single-player experience, so these games mesh nicely with the Wii's strengths.
Yet DLC, especially in the Microsoft/Sony conception, is often misused. The most ridiculous example by far is ludicrous horse armor expansion for Oblivion, which is exactly what it sounds like -- armor for your horse. And it cost 500 Microsoft Points, or $6.25. This is the sort of thing that should have been packaged with the original game, released for free, or just not included at all. More broadly, DLC is too often being used as a way to make more money on a game by making the consumer pay extra for parts of the game that should have been included in the original title, rather than a true expansion upon an already-complete title.
It is in essence a sign that gaming has entered what I consider to be the second stage of its life: programmers and artists are having increasingly less reign over how a game is presented, while business people are gaining ground. To be fair, the struggle between art and commerce is basically as old as art, but to see it encroaching upon interactive entertainment perhaps makes the point a little closer to home than one might expect.
And yes, game companies do need to make money to keep making games, and many also have shareholders to answer to. But DLC, especially as Sony and Microsoft have (generally) presented it, too often has the reek of Excel spreadsheets and a boardroom speaking of profit margins about it. And in the long run, if enough people wise up, this may actually hurt companies.