Yeah, me too. It is sad, but I guess there's no way to compete with DTRPG/RPGNow. Paizo does OK, though -- I'd guess it helps that they're the #1 RPG these days and you can't get their stuff on DTRPG!
Sales figures are interesting. 90% of my PDF sales are DTRPG/RPGNow, 10% are Paizo.com, and at YGN I sold exactly one PDF in the six years I had products there. On the flip side, those figures are definitely affected by the fact that I have twice as much product at DTRPG as Paizo (I don't try selling 4E stuff there, for example), and had only five products up at YGN. That undoubtedly reduced my sales figures there.
I did try the PFSRD.com store (they kindly agreed to upload my entire product library at the time). I was there for about 6 months, I think, and didn't sell a single item. I did get lots of emails from them about how great their overall sales figures were, though, so I guess that's nice for them!
All that aside, not only is it not likely that a new company could compete with RPGNow/DTRPG, uploading an entire product catalogue to a new site on the off-chance of selling 3 PDFs a year isn't something most publishers, including me, are likely to do. So I guess it's partly our fault.
I often wonder if a new USP could work. A site dedicated to subscriptions and periodical products (adventure paths and the like) could work. DTRPG has a subscription system, but it's not very well featured; Paizo doesn't have one at all that third parties can use. If someone had the start-up capital, I think they might be able to make a subscription service work where publishers sell monthly subscriptions and customers get periodical content in PDF format. e-Magazines, adventure paths, that sort of thing.