Do Xbox (Series/One) Games Work on Xbox 360? No — Backward Compatibility is One-Way

No. Xbox Series X|S and Xbox One games are not playable on Xbox 360.

Why

• Different Architecture: 360 = PowerPC (big-endian); One/Series = x86-64 (little-endian).
• Different OS: 360 runs a custom NT-based kernel; One/Series run Windows-based Hyper-V host + Game OS.
• Different Disc Format / Encryption: 360 uses DVD-DL (XGD2/3); One/Series use Blu-ray (BD-R) with different file system and signing.

Backward Compatibility is One-Way

• Xbox 360 games → Xbox One / Series X|S: Yes, ~600 titles via software emulation (digital or disc).
• Xbox One games → Xbox 360: Impossible.
• Original Xbox games → Xbox 360: Partial (emulation, ~400 titles).
• Original Xbox games → Xbox One / Series: Yes (subset of 360 BC list).

If you want to play current-gen games, you need an Xbox One or Series X|S.