If you loved Code Geass: Lelouch of the Rebellion II - Transgression, try Mobile Suit Gundam I
A bridge between a film you've already seen and one most people haven't. Here's what they share, and what the second one does that the first one doesn't.
You already loved

Code Geass: Lelouch of the Rebellion II - Transgression
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Mobile Suit Gundam I
What they share
Theysit in Action / Animation / Science Fiction territory. If that's the register that drew you to Code Geass: Lelouch of the Rebellion II - Transgression, the second film will land in a comparable space — through a different lens.
What Mobile Suit Gundam I is
You wake aboard a space station in the UC 0079 era when Zeon declares war on the Federation. Then the colonies start falling. The film stops to watch a boy survive the first battle between humans and machines.