Westerns ebb and tide just like vampire shows it seems. The late eighties and nineties it seems had a lot of westerns serials. Though all weren't that bad, had promise, and were fairly respectable, only Dr. Quinn and if you count Christy had a solid run. Perhaps that was more of this 'appeal to women' western vibe that those had, but The Young Riders, Brisco County Jr, The Magnificent Seven, Dead Man's Gun, and Deadwood didn't run nearly as long as they could have.
It wasn't the shows, just ratings and budget that killed them. I don't think westerns are as much as a niche as they are made out to be, but merely too expensive and demographically small for networks to bother.
Dead Man's Gun isn't on dvd, but you can find Dr. Quinn and Christy on tv now. The others I'd like to get on dvd at some point, too. I suspect the only way a western might come back would be if it was as some sort of anthology style on cable, with one or two characters traveling or such. Does that make Renegade count? Deadwood's cast was huge.
Actually, what does everyone think of Walker, Texas Ranger? I never cared for it. Maybe it wasn't always a hit, but I think Chuck Norris' own money probably helped it last as long as it did.
Episodic westerns are expensive, but AMC and TNT used to produce and show a lot of the Louis L'Amour adaptations with Tom Selleck and Sam Elliot. Personally, I love classic westerns but I can see how they're not for everyone.