If you liked the Yu-Gi-Oh! anime, the Anime-Planet community thinks you'd like:
For Niwa Daisuke, turning 14 should be accompanied by romance and the promise of new adventures into adulthood, but instead comes with a surprising revelation: all male children of the Niwa's bloodline inherit the powers (alter ego) of Dark, a phantom thief, upon their 14th birthday! Now, in addition to his ever-present quest to win the heart of his childhood friend Risa, Daisuke must commit acts of thievery (with his doppelganger Dark controlling his body), to steal mysterious pieces of art for unknown purposes. For Daisuke, his growing pains are just beginning!
Although there is not much similarity between the plots, both anime like to mix humor and seriousness. The most important reason for this recommendation is because of the similarity between the protagonists: both Daisuke and Yuugi are typical 'uke' characters, being not really manly, short, and viewed as girl-friends of the girls. Moreover, both characters have other, much older personas sealed in them, who are not only more 'cool', but are more popular with the girls (in both cases the girl the protagonist is in love with) and are smarter than their vessels: Yami is excellent at games, winning anything he tries, while Dark is a thief the police cannot catch, no matter what high-technology they use.
One more similarity is that both have a pair - another person that has a person sealed inside them, and that is the arch-enemy of Yami/Dark. In both cases, the vessel of the evil is not someone who wishes to harm Daisuke/Yuugi.
Twelve-year-old Shobu Kirifuda has one goal: to become a top-ranking player at the game of Duel Masters, a card game in which players use spells and summon monsters to break through their opponents' shield cards and subsequently defeat them. Shobu believes he's a great player, but he soon discovers that there is more to the game than he originally thought; true Duel Masters, he learns, are able to make the monsters on the cards manifest themselves during a duel. A mysterious group has taken a keen interest in Shobu, although their reasons are as mysterious as the group itself. Now Shobu and his friends not only have to win the championship, but also try to figure out who these people are and why they're so interested in Shobu.
Shuzo "Shu" Matsutani is young, loves baseball, and carries around a useless white toy called a Talispod - at least, he THOUGHT it was useless. What Shu soon discovers is that Talispods can summon powerful monsters known as Legendz stored inside of Soul Dolls, and the evil Dark Wiz Toy Company wants his Talispod for nefarious purposes. After being chased by Dark Wiz's lackeys, Shu receives the ultimate gift from the skies: a Windragon who will fight by his side. Now, with the help of his friends, Shu will become involved in battles, hold back the Dark Wiz Toy Company, and discover the locations of the remaining Soul Dolls.
Both anime are about friends banding together for one purpose - to show the power of friendship to those who would a oppose them. They are also concetrated on a sacred power given to the main character - who is small but gains strength of heart - to guide the main character and his friends.
Some time ago, Jin Mitaka lost his memories when battling against Count Pythagoreas. Now that the Orpheus Order has been defeated, Kaito, Nonoha and Rook are determined to restore the man to his former self by bringing him to familiar locations, and soon arrive at the Fool’s Puzzle from their past. But things escalate when a mysterious girl named Raetsel ambushes them in the puzzle’s chambers; she works for an organization called Master Brain, and she’s come to steal Jin away. And not only does Jin recognize the girl, but she also claims that Master Brain’s goal is to rid the world of puzzlers at Jin’s request! Now, it’s up to the Children of Phi Brain to discover the truth and put a stop to the organization’s nefarious plans.
Both anime series feature various puzzles (= deadly games), where people are punished for failure and are mostly episodic. Do note that the YGO! series I have in mind is the original one with 27 episodes.
The mystery of "The Blade Children" is a secret which has remained well-hidden, and has cost some their lives. After Narumi Ayumu's brother disappears in a search for the answer, Narumi is forced to unravel this mystery for himself. Join him in his investigation which will lead him to the secrets of the Blade Children, and to tests of skill which may prove to be fatal.
While the original Yu-Gi-Oh! is entirely different than the card game series, it feels close to Spiral, since it doesn't have much to do with the card game yet, which makes it a lot more serious.
Both series are about smart games of life and death, and they have a specific feeling to it, which is rarely to find anywhere.
If you like the atmosphere in one, you'll probably like the other one as well.