The areas where 3rd parties excel, are those areas neglected by WotC. Original settings, d20 variants, that sort of thing.
I don't think Charles Ryan meant to say that WotC is better than all third party publishers. I think he meant that no other 3rd party publisher is going to be able to compete with WotC in terms of making core 3.5 compatible sourcebooks. Which is basically true.
However, although what Ryan says is sort of true, there is a critical fact missing. Most d20 publishers don't even really compete with WotC anymore. Its easy to be the number 1 publisher of generic 3.5 D&D sourcebooks when no other publisher is making those books anymore.
The survivors of the d20 bust have become quite specialized and focused. I go to Green Ronin for M&M or to AEG for Spycraft, or Mongoose for Conan. These are great products filling a niche that WotC is not.
And when people talk about adventures selling or not selling, I think a distinction needs to be made between modules and campaigns. Modules don't sell. But I think there is a seriously massive untapped market out there for complete level 1 to 20 (or beyond) campaigns. But let me put a qualifier on that. I don't think any old hodge podge of adventures from El Cheapo games will work. Gamers want high quality. And they want to be able to play a continuous story from low level on into high level without a drop in quality.
My group could care less about your average module, but when Shackled City came out, we were all over that. Shackled City is a busy DM's dream come true. Well written, well edited, glossy full color pages, professional maps, and even player handouts! This is how you sell adventures!!
Is it expensive? Yes, but worth every penny and it allows us to take our PCs from level 1 to 20 all with minimal work on the part of the DM. And even better, is the adventures are somewhat episodic becuase they came out of Dungeon magazine. This means that if you take a month off from DMing, you don't have to reread the entire freaking book to refamiliarize yourself with everything. You just reread the adventure you stopped on. Brilliant!
I truly hope Paizo has started something big here.