Babylon 5 Viewing Order

“To answer your question, I believe you should watch them (more or less) in the order in which they were aired. IMO, the only reason to watch In the Beginning earlier than its original broadcast is if you need convincing of how incredible the story is before sitting down to watch. If you’ve already made up your mind to watch the show, no sense spoiling stuff that’s much better when revealed slowly over a few seasons. You say you’ve already seen up to Season 3, so I guess it doesn’t matter too much.

Also, while ‘Sleeping in Light’ does take place chronologically after River of Souls and A Call to Arms, I’d recommend watching it right after ‘Objects at Rest.’ This is certainly debateable, but unless there is a compelling reason otherwise (the network shuffled the eps or something), I tend to lean towards watching things in the order in which they were broadcast. I think ‘Sleeping in Light’ works best as a one-two-three with ‘Objects in Motion’ and ‘Objects in Rest’.

If I were building a definitive order, it’d likely go like this.

The Gathering
Season 1: Signs and Portents
Season 2: The Coming of Shadows
Season 3: Point of No Return
Season 4: No Surrender, No Retreat I
Thirdspace (Either directly after ‘Into the Fire’ or after ‘The Illusion of Truth’ … anywhere between ‘Into the Fire’ and ‘No Surrender, No Retreat’ would be fine though)
Season 4: No Surrender, No Retreat II
In the Beginning
Season 5: Wheel of Fire (I’d watch ‘Phoenix Rising’ before ‘Day of the Dead’, even though their aired flipped - doesn’t really matter as ‘Day of the Dead’ is a stand-alone, but it flows better that way)
The River of Souls
A Call to Arms
Crusade
The Legend of the Rangers

Hope that helps.”

das

Source: DVDTalk