Re: Battlestar Galactica: just past halfway
BSG is worth watching... once through.
I stood and looked at the season sets at Sam's Club at $19 a box and almost bought them... then passed. I don't see us every re-watching it (nor Sopranos, nor Rome, nor Mad Men - some things are just "once and move on").
B5, on the other hand, I once taped and watched and wiped, then taped and edited into a complete set (4 eps, no commercials, per tape)... then bought the DVD sets, and we rewatch it starting, oh, every 18 months or so. For all its flaws (uh, you call those sets?) it is perpetually engaging and the small bits you forget are endlessly re-entertaining. The incredibly satisfying solidity of the story line is a treat in itself.
BSG has 50% better production values, enormously better guest and supporting actors (some B5 guest stars were painfully bad, even some big names), Edward James Olmos in a simply mesmerizing role and performance, and some intriguing concepts. But the story wandering around into disconnected nonsense and obviously heading nowhere but to the next script conference makes it a one-time deal.
BSG also falls for some terrible "trouble with the doubletalk generators" plots - we just watched one where two lead stars were trapped in an airlock, and the problem could have been resolved by any teen Heinlein Hero in about four seconds flat. But... a VERY capable character, two of them really, couldn't figure out how to plug a pinhole air leak, leading to a very dramatic but 472% overblown rescue.
I'd say spend a few months watching it through, via Netflix or whatever. B5 will always be there waiting.