I'm sort of in the same camp with RFisher. I think that, if adventures were tailored to different niches of the market, then they would work out better. WotC's main modules, the Adventure Path, are a good example. Sunless Citadel was very popular, a good leader that mixed dungeon crawl, roleplaying, politics, and all kinds of different challenges. Then there was Forge of Fury, a standard dungeon crawl. Then Speaker in Dreams, a city adventure with mostly smaller encounters that sort of tied together.
See where I'm going with this? These were all different types of adventures, which should have been meant for a different type of audience. But they weren't presented that way- they were all part of the same series, and it was just assumed that people would buy them all, regardless of adventure type and theme. I don't think this was the case, because different groups like to play different sorts of adventures.
For example, I dislike dungeon crawls. I'm also getting fed up with the endless amounts of demons, undead, and evil humanoids that are appearing in modules- they're just generic villains with no motivations at all, other than half-baked Bond villain schemes. As a result, I don't buy that many D20 adventures. I especially don't buy Dungeon magazine. But that's just my particular demographic- it's obvious that there's a lot of people out there who like and have a use for what Dungeon is doing. I'm simply not one of them.
I think that WotC could do a good series of modules if they seperated them by theme, rather than by brand or setting. For instance, there could be a "D" series of modules that are just dungeon crawls- Goodman Games has had great success with these (even I, dungeon-hater that I am, have bought a couple). Then there could be a "U" series for urban adventures, and perhaps an "L" series of drop-in locations with smaller adventures (such as Standing Stones or the Whitethorn series).
So, to sum up, I think there's a lot of potential for generic adventures that are marketed to play styles, rather than cramming a bunch of different play styles together under a setting label. If Wizards were to put out a line of modules that worked for my game, I'd probably buy them all. As it was with the adventure line, I only bought three (and only got Bastion because I happened to need a nasty red dragon encounter).