Immortal male leads chase other immortals all the way from the ancient past into post-apocalyptic dystopian futures, armed only with their swords, and find themselves involved with resistance groups. In both love is the driving force but where they differ is Highlander's driven emphasis on revenge as its lead, Colin, gets his arse kicked for 1000+ years by his immortal arch-nemesis, Marcus: the man responsible for killing the woman he loved. Kurozuka just has its lead fight people as he desperately searches for his immortal woman; trying to unravel the mystery of what happened before he woke up in a bleak future.
Madhouse created both titles. Highlander has Kawajiri's distinctive action flair and is far more focused as a movie than Kurozuka is as a TV series. In fact, Kurozuka is all over the place after its two excellent / stylistically-gruesome first episodes.  read more
Both are made by Madhouse Studios and directed by Yoshiaki Kawajiri. They are both deal with stories of revenge and are very action pack. Both movies have tons of sword fights, blood and gore. Highlander: The Search for Vengeance feels like a true sequel to the first Highlander film and feels like a modern anime made for old school anime fans. If you enjoyed one, you will enjoy the other.
I don't want to say to much, but they both feel similar. The main characters are both pretty much Immortal and have inhuman powers. The movies are packed with action and gore. The characters are also pretty similar, very hard and silent type with no feelings.
Afro Samurai too is about a story of revenge. They are both pretty violent but Highlander lacks the intensity of the swordfights and can't get even close to the eye-catching style Afro Samurai got. Both shows are originally dubbed in English but while AFs voice acting is convincing and well done Highlanders sounds dull and artificial.