A part of me wonders how much of it is just marketing. If most AA games got the marketing push a WoW expansion or Madden 45 got, then I'd imagine there would be a greater volume of sales, though who knows if the net profits would pay for the marketing. So the digital distribution landscape is great for both the indie and middle market. No shelf space to argue with retailers about, and the various ways that digital stores can showcase games or provide connections to similar games certainly helps the buyer to see something that maybe they wouldn't know about otherwise. That and forums/ word of mouth is how I've gotten connected to a lot of great games.
But as others mentioned, from a purchaser standpoint, its tough sometimes. You can get the big well advertised games from a year ago on sale pretty regularly. Do I spend my 40 bucks on a couple games that were all over tv last year? A new AA game? A handful of indie games? Save up for the next best thing that everyone is salivating over but may be terrible when it arrives? I've tried a bit of it all and still don't know.
I do think that the middle market tends to have the most consistently interesting games. Indies might have a single great idea they run with, but they tend to be too short or repetitive to have lasting replay. I love em, just don't keep going back year after year . .and there's almost never a mod for an indie. The AAA that lives up to its hype is great, though great production values have the downside to those of us that still love modding . . .full voiced characters in RPG's and high end gfx has really hurt the independent modder. More often I wonder where the money went, and since the AAA is locked in the world of "not too complex" and "not over 40 hours . .in fact 10 hours is better than 60" it does rankle a bit. Middle market seems to be more willing to try something different, and enough money behind it to flesh it out. Do something that breaks the mold a bit, something long or complex or PC only. The modding community is generally much better supported as well, and to me mods are huge. A great way to help a game continue to have value after years, or make an okay game great.
It also feels like a cycle. I remember when space flight sims were huge, and had the early AAA hallmarks of in game movies with popular Hollywood actors and the like. They were marketed and hyped and were big buisness, then bam, the market died. The whole flight sim genre is largely dead from a AAA standpoint. But the middle market keeps it alive. The wheel slowly comes around. The traditional complex RPG was kept alive in middle markets, and Bioware brought it back to AAA with DAO. Did great, huge sales, game of the year. DA2 tried to become a bit more AAA popular minded, and there seems to be discontent. In that, there may be a hint. I think that what a lot of people *want* is a AA style game from a design and gameplay standpoint. .just with the AAA potential for the latest greatest graphics, voicing, or polish. Not that you're guaranteed to get that anywhere.