I don't know, the only person I know who saw BSG and Lost loved both endings, but *I* haven't seen BSG so I can't judge (though it's high on my to-watch list).

Re: the Lost ending - without spoiling anything, I know that if I was told it ended like this while I was watching the first season, I would have stopped watching straight away. BUT coming to it after the whole journey I positively liked it. Judging from the reactions around, I guess that those who liked the finale were those who put the characters' stories first, while those who focused on the mythology/sci-fi elements were disappointed. And the storytelling IS uneven - you can see which plot threads had been planned since the beginning and which ones were born (or died) because of contingencies; some of them become interwoven with the main plot so well you can't believe they were introduced in progress, others are blatant dead ends. But of course, well, you know I'm a total Lost junkie, to me the good trumps the bad. And I think that thematically the series has been really consistent - the ending is like the final illustration of things the characters have been saying since S1, which finally play out.

And sorry for the tl;dr ^^;