[nkoren]

Five seasons and a number of TV movies:

http://www.midwinter.com/lurk/countries/us/eplist.html

The "P5 rating" for each episode tends to be a very reliable indicator of its quality. That said, B5 cannot be watched out of sequence, and there are very few episodes which one can skip, due to the nature of the story arc.

[angersock]

You can skip most of the first season without too much detriment, maybe up until the last six episodes. It had a lot of onboarding, and honestly served mainly to get audiences used to the style of the universe and that things were not just rubber-mask villain-of-the-week nonsense (the passing of Ivanova's father, for example).