Whereas Babylon 5: A Call To Arms is the beginning of a new adventure in the Babylon 5 universe, Babylon 5: In the Beginning actually completes the epic story that is introduced to us in Babylon 5: The Gathering and then continued by the television series.
Babylon 5: In the Beginning describes the events leading up to the Earth-Minbari war in context with everything we have seen in the TV show. For those of you that don't know, the Earth-Minbari war happened 10 years before the start of the time line of the show. The TV series then proceeds to tell the story of Babylon 5 year by year from then on.
Babylon 5: In the Beginning has a fantastic story, and it introduces us to one or two wonderful new characters. It is brilliantly put together, but just like Serenity (The Firefly movie), Babylon 5: In the Beginning makes much more sense, and is much better, if you watch it after watching the TV show. I suspect that is why it has such a relatively low score here on IMDb; perhaps many viewers had not watched the TV series first.
In the Beginning also contains spoilers for the TV series. Delenn, Sheridan and G'Kar's characters, for example, are very much in keeping with the characters as we know them towards the end of the TV series, not as they are in the first two seasons. You could argue this is a negative point but it falls within the scope of artistic license, and it is hard to imagine how it can have been done any other way. So I think you really need to have at least watched the first four seasons of Babylon 5 before watching In the Beginning, although personally I'd recommend watching everything from the TV show before watching this (don't forget to start with Babylon 5: The Gathering).
Babylon 5: In the Beginning describes the events leading up to the Earth-Minbari war in context with everything we have seen in the TV show. For those of you that don't know, the Earth-Minbari war happened 10 years before the start of the time line of the show. The TV series then proceeds to tell the story of Babylon 5 year by year from then on.
Babylon 5: In the Beginning has a fantastic story, and it introduces us to one or two wonderful new characters. It is brilliantly put together, but just like Serenity (The Firefly movie), Babylon 5: In the Beginning makes much more sense, and is much better, if you watch it after watching the TV show. I suspect that is why it has such a relatively low score here on IMDb; perhaps many viewers had not watched the TV series first.
In the Beginning also contains spoilers for the TV series. Delenn, Sheridan and G'Kar's characters, for example, are very much in keeping with the characters as we know them towards the end of the TV series, not as they are in the first two seasons. You could argue this is a negative point but it falls within the scope of artistic license, and it is hard to imagine how it can have been done any other way. So I think you really need to have at least watched the first four seasons of Babylon 5 before watching In the Beginning, although personally I'd recommend watching everything from the TV show before watching this (don't forget to start with Babylon 5: The Gathering).