Is there way to come up with a list for popular blog posts in Grav?
For create a popular blog posts plugin you can use a views or replies, for views I have already write a simple plugin, for the comments using the external comments system is not simple to get all page comments.
I already have a plugin that is part of the upcoming admin plugin. This provides some simple statistics tracking. One of those will allow you to see the popularity of posts/pages. It’s not quite ready yet though, but stay tuned to new of the admin plugin.