I have great fondness for how we, as a family, used to watch season one of Babylon 5 every week in a slightly mocking "It's a bit rubbish but there's nothing else on at tea time and the effects are pretty" way, only to be completely addicted by the end of the year (it should be noted that the UK broadcast wasn't helped by the pilot not being shown until after season one, as a bank holiday special IIRC).
In retrospect most of the first year is perfectly fine 90's US SF TV with a handful of stand-out shows (Signs and Portents, Babylon Squared, the final). The big problem is, whilst the aliens pretty much hit the ground running the humans tend to find a lot longer to find their feet, with Jerry Doyle being the only one to really give a consistently good performance from the off. Poor old Michael O'Hara never really gets a chance to settle down, most of the time being very wood like with random moments of Shatner thrown in.
Season 2 does kick things up a gear, and season 3 builds to one of the all time best TV cliffhangers. But my favourite is the fourth, the cancellation forcing JMS to wrap things up a year early means the year is all killer, no filler and builds up to a great climax.
Sadly that means we then get the un-cancellation, which coupled with the fact burn out from writing that many episodes is begining to hit JMS means season 5 starts of badly, and even when it starts to pick up again (the Londo and G'Kar stuff is at least as good as anything else in the show) it's still wildly incosistent. Without going into spoilers, the new set up introduced at the end of season 4 never really works for me.
With the movies, In The Begining is best (albeit suffers from an important actor from season 1 of the show only being involved in stock footage, meaning he suddenly comes out of nowhere to end the war with no connection to anything else in the film, making it pretty much for the dedicated fan only), Thirdspace is good silly fun and A Call To Arms is a surprisingly decent back door pilot, but suffers from knowing now none of it will ever go anywhere. River of Souls is pretty much terrible, and only really interesting as a snap shot of where Martin Sheen and Ian McShane's careers were before The West Wing and Deadwood came along.
Never really bothered with Crusade as the bit I did see didn't convince me JMS was over his burn out. And I managed about half an hour of Legend of the Rangers, as others have said G'Kar is the best thing in it. And even he seems oddly off, like he's smoked a big pile of dope just beforehand.