If you liked
Touhai Densetsu Akagi: Yami ni Maiorita Tensai
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...then you might like
Gyakkyou Burai Kaiji: Ultimate Survivor
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Both series are by the same author and contain similar themes (gambling/challenges). Akagi seems more mature at first, but I'd say both are on equal footing by Kaiji's second season (and you should watch both). Art is pretty much the same, except improved on Kaiji, and both have OSTs that suit the theme of their respective series.
If you liked
Cross Game
|
...then you might like
Diamond no Ace
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Diamond no Ace is an improved version of Cross Game IMO, not because the story is similar, rather because it deals with similar themes (growing up, hardship, being away from loved ones) while presenting them in a much more polished manner. The baseball aspect is also much better explained and dealt with in Diamond no Ace.
If you liked
Shinseiki Evangelion
|
...then you might like
Mahou Shoujo Madoka★Magica
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These two anime are similar in the sense that they break down stereotypes and bring something refreshing to the viewer. Both have some unexpected plot twists and very sad moments. Characters face dreaded circumstances and go through emotional pain.