After reading some AWS documentations, I am wondering what's the difference between these different use cases if I want to delivery (js, css, images and api request) content in Asia (including China), US, and EU.
Store my images and static files on S3 US region and setup EU and Asia(Japan or Singapore) cross region replication to sync with US region S3.
Store my images and static files on S3 US region and setup cloudfront CDN to cache my content in different locations after initial request.
Do both above (if there is significant performance improvement).
What is the most cost effective solution if I need to achieve global deployment? And how to make request from China consistent and stable (I tried cloudfront+s3(us-west), it's fast but the performance is not consistent)?
PS. In early stage, I don't expect too many user requests, but users spread globally and I want them to have similar experience. The majority of my content are panorama images which I'd expect to load ~30MB (10 high res images) data sequentially in each visit.
Cross region replication will copy everything in a bucket in one region to a different bucket in another region. This is really only for extra backup/redundancy in case an entire AWS region goes down. It has nothing to do with performance. Note that it replicates to a different bucket, so you would need to use different URLs to access the files in each bucket.
CloudFront is a Content Delivery Network. S3 is simply a file storage service. Serving a file directly from S3 can have performance issues, which is why it is a good idea to put a CDN in front of S3. It sounds like you definitely need a CDN, and it sounds like you have tested CloudFront and are unimpressed. It also sounds like you need a CDN with a larger presence in China.
There is no reason you have to chose CloudFront as your CDN just because you are using other AWS services. You should look at other CDN services and see what their edge networks looks like. Given your requirements I would highly recommend you take a look at CloudFlare. They have quite a few edge network locations in China.
Another option might be to use a CDN that you can actually push your files to. I've used this feature in the past with MaxCDN. You would push your files to the CDN via FTP, and the files would automatically be pushed to all edge network locations and cached until you push an update. For your use case of large image downloads, this might provide a more performant caching mechanism. MaxCDN doesn't appear to have a large China presence though, and the bandwidth charges would be more expensive than CloudFlare.