It's interesting to note that, at least in 2008, Microsoft has been hesitant in all but a few cases of allowing full-sized download games on its service. But Sony has not been so restrictive -- and consequently, has opened its service up to games that push the boundaries.
Thus, we've seen PS3 re-releases of games that were previously available at retail (Burnout Paradise), those with niche appeal (NFL Head Coach), those which couldn't support a retail release but exceed the scope of an average download title (Wipeout HD), and those that are available at retail in other territories but become download-only products in North America (Siren: Blood Curse).
Each of these cases points to an exciting future for the download market on the PlayStation 3 and, as standards inevitably change on the Xbox 360 and advance in further console generations. We may obviously see a future where games that would previously have gone to retail on discs are now available as downloads. (Microsoft does currently allow download of Xbox Originals titles on the 360, despite their prior disc-based nature as Xbox 1 titles -- an important and often overlooked facet of Xbox Live.)
This service, of course, also in full swing with Sony's PSP as well -- with Echochrome, again, being a download-only title in North America despite being out on disc in Japan and Europe. This alternate delivery mechanism will, as it has on PC with services like Steam, only continue to gain ground on consoles.
We've already talked about how microtransactions are going to become more significant to the MMO marketplace as time wears on. But the stratification of the online game market may be an even bigger and more significant trend.
With the triple-A staying power of World of Warcraft the crown jewel in the subscription-based marketplace, the games that compete with are trying one of two things -- a gigantic all-out WoW-rivaling mega product, or an attempt at an entirely different, niche experience or business models.
Nexon's 2D, anime-inflected MapleStory attracts a younger audience with less cash; EVE Online maintains a base of hardcore subscribers; free-to-play Guild Wars makes money on retail expansions and continues to flourish.
Other Asian MMO ports, while lacking in critical mass, can fill the cracks by appealing to niche audiences -- with games that have already been developed. So sure, there's still a core of big-budget MMOs going for a direct $15-per-month run against Blizzard. But those that are there are increasingly using existing IP (Star Trek Online, Warhammer/Warhammer 40k) to stand out.