Mega-Puppeteer vs. Kzinti-don?
I've actually not watched anything other than BSG on Siffy in a decade or more... the reports about the Riverworld atrocity kept me away from their Dune ones, though I've heard OK things about those.
Dune was OK but dull. Children of Dune was actually rather good.
Have to admit, while I've seen both live adaptations of Riverworld I've yet to read the book they're based on, so I can't say how well or poorly they treat the source material. Having said that, I'm at a loss as to why people felt the need to tackle this one twice. Doesn't seem that interesting at all. Is there some major subtext from the books that they both miss? I just don't get it.
As for Ringworld & Childhood's End....given SyFy's track record these last five plus years, I can't say I'm holding out much hope. Mind you, while the concept for the Ringworld itself is of course hard sci-fi, as a story it's pretty standard adventure fair. So there's not much to get wrong in terms of content. Plenty in terms of tone, casting and direction of course. Personally, I anticipate dullness.
Childhood's End is a totally different animal. I'm not sure how they'll approach it--much less how they'll get a way with having millions of naked children dancing around. Again, the tone of the thing is key.