I've watched the miniseries and season 1 on DVD, and thoroughly enjoyed it. My memories of the original series from when I was much younger are pretty vague, and from what I do remember it was enjoyable but wasn't that compelling; actually, it's kind of mixed up with Buck Rogers :-). The "re-imagined" series is a complex, rich story following a well-defined story arc—a strategy that worked wonderfully with Babylon 5—with a dark, gritty feel... it's truly entertaining. Best small-screen SF in a long while!
Talking of small-screen SF... I've got to say that the first season of the latest Doctor Who really didn't do much for me. My favourite doctor remains incarnation #4 (Tom Baker). The (much) earlier series had a more serious tone, and while there was humour, it was clever and toned down. There was also a surprising amount of violence; it's amazing the kind of bodycount that could be accumulated with so little blood'n'gore, thanks to the prevalent use of energy weapons. The modern versions—from around doctor #6 and onwards—have tended towards the "Benny Hill" side of British comedy (which I despise).
I've heard good things about season 2, with the incarnated-once-more doctor apparently doing a much better job, so I suppose I shouldn't give up hope!