Ninja Batman

Both are vengeance themed stories focusing on samurai type characters and share settings that mix in feudal and modern japan like aesthetics as well too.  

Batman in another world. While "Ninja Batman" involves time travel and the Caped Crusader himself, "The Eminence in Shadow" features a protagonist who can fit the bill of a Batman fanboy being isekai'd to another world and lives out his Dark Knight fantasies. 

Ninja Batman takes a lot of inspiration from Gurren Lagann, and it is heavily recommended to watch TTGL prior to Batman to better understand what is going on in the movie and how. 

Both are movies with stellar animation, great character designs, good voice acting, fun characters (for the main few), and have a climactic, bombastic ending that is sure to excite any person watching it. 

Iconic and famous stories retold in a new medium with plenty of style and character while still staying relatively true and respectful to their origin 

I'll let someone else fill in the obvious recommendations of other Studio Trigger/Gainax works, but if you love how ridiculous either of these movies get in their final acts, you'll most likely enjoy the other one. In short: After an already surreal premise in both movies, giant robots suddenly intrude and drive the plot to its conclusion.