If you liked the Detective Conan Movie 10: The Private Eyes' Requiem anime, the Anime-Planet community thinks you'd like:
When a group of children discover a strange cave at the beach, their lives are forever changed. Inside they find a hide out filled with computers and a man named Kokopelli who gives them a curious offer: to participate in a special game in which they save Earth from fifteen giant monsters. To defeat the invaders, he will give them a powerful mecha of black armor. The children eagerly sign the contract, name their new weapon Zearth, and must now take turns to pilot it; but the 'game' is in fact all too real and the consequences of battle become the stuff of nightmares. With no option to cancel the contract, is there any way to stop the game before it is too late for all of them?
This is a BIG stretch, but since the majority of the recommendations for anything Detective Conan will be the same detective titles, I thought something new to the mix might be helpful.
Bokurano has similar story elements to Conan Movie 10; the main characters are trapped in a "game" that has deadly consequences, and they try to do whatever it takes to win (or find a way to not die). Again, it's not a straight detective story, but if you enjoyed the story elements of Conan Movie 10, you could try on Bokurano for size.
Fudou Academy's Hajime Kindaichi is the grandson of the famous detective Kousuke Kindaichi. Though he often appears to be lazy in school and clumsy, he is actually a modern-day genius with an IQ of 180. Together with his childhood friend Miyuki, Hajime solves the most unsolvable murder mysteries with ease and grace. From missing students to wax museums, there's no case that Hajime Kindaichi can't solve!
Fans of the murder mystery episodes/movies/OVAs of Detective Conan would definitely appreciate Kindaichi (and its movies). Kindaichi has less of a lighthearted feel and would certainly appeal to the same fans.
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.
Though I don't believe Spiral is a good recommendation for all things Conan, I definitely think it fits well with Movie 10. Both are detective dramas of course, but both also specifically have deadly consequences and are, at their hearts, thrillers. If you liked one, try out the other.