This Sunday, the British series Merlin, a re-imagining of the Arthurian legend, premieres on NBC, with a cast of actors mostly unknown on this side of the pond. (The notable exception being Anthony Head from Buffy the Vampire Slayer.) But is America ready for a new medieval television series? Sure, Legend of the Seeker just got renewed, and Robin Hood airs on BBC America, but is period fantasy ready for one of the big networks? We took a look back at previous period fantasy shows to see whether they were hits or misses.