To ensure that game assets are fetched from the closest region and have a fallback option in case the assets become unavailable in the closest region, a solution architect should leverage Amazon CloudFront, a global content delivery network (CDN) service. By creating an Amazon CloudFront distribution and setting up origin groups, the architect can specify multiple origins (in this case, the Application Load Balancers in each region). The primary origin will serve content under normal circumstances, and if the content becomes unavailable, CloudFront will automatically switch to the secondary origin. This approach not only meets the requirement of regional proximity and redundancy but also optimizes latency and enhances the gaming experience by serving assets from the nearest geographical location to the end-user.

AWS Documentation on Amazon CloudFront and origin groups provides detailed instructions on setting up distributions with multiple origins for high availability and performance optimization. Additionally, AWS whitepapers and best practices on content delivery and global applications offer insights into effectively utilizing CloudFront and other AWS services to achieve low latency and high availability.