I too am really taken aback by this claim of poor acting in Babylon 5. Sure, Claudia Christian and Pat Tallman aren't Meryl Streep, but, they do a fine job as the characters they play. The rest of the principals are all great actors, IMHO (as well as several of the recurring actors who played multiple roles such as Kim Strauss and Wayne Alexander).
Certainly, some of the acting is more like a stage play than TV, and more formal and Shakespearean, but, I don't think the acting is poor in the slightest.
One Day I hope to be the Man my Cat thinks I am
Where are we going? And why are we in this Handbasket?