 If you liked Shaman King |  ...then you might like Fate/stay night |
Fate-stay night has a number of similarities to Shaman King, but as a seinen series is overall darker and more character-focused. Magic takes on a larger role in F/SN than Shaman King. Both series revolve around a tournament fought with spirit allies over an incredible power.
Both series have story about summoning people from the past and use it for battle/tournament.
Both are about a battle between Magi/Shamans that held per long period of time, battling each other using Spirits of warriors of the past. a battle which only the last one standing is the winner. To win the Holy Grail/Holy Spirit, something that gives the power to achieve one's dreams. What are the characters dreams and goals? And why they are participating in these battles? Are these Servants/Spirits just tools to win the battles? Both series hold these questions. However, Shaman King is more about friendship, it's lighthearted with mush comedy. While Fate/ Stay Night is darker and focuses more on characters development with some romance.