I think the actors in B5 do a fine job, but I also think many of their performances could have been better directed and the dialogue better written. Much of it just sounds very unnatural.
As far as guest actors, I'll give you Marjorie Monnaghan, she probably should've chosen a different career, she's great as an action hero, but, her line delivery leaves an awful lot to be desired in any role I've seen her in
One Day I hope to be the Man my Cat thinks I am
Where are we going? And why are we in this Handbasket?