you missed the biggest one:
browserify 2,218,006 downloads in the last month
But my prediction is Rollup will take off in a big way at some point in the next 2 years. It's not quite stable enough yet, but it's just fundamentally better designed than everything else. Rollup is the only tool I'm aware of that properly exploits static analysis of ES6 module syntax. Every other bundler is full of hacks and moving parts, Rollup's codebase is clean and beautiful. It's already very good for bundling ES6 modular code, it's just still got some kinks when it comes to integrating people's CommonJS code. And I guess not enough people are actually using module syntax yet for Rollup to come into its own, which is a chicken and egg problem. It will get there though.
Until Rollup is stable enough, I recommend Browserify. In my opinion Webpack and JSPM both try to do too much and are too prescriptive about workflow. My team switched from Browserify to Webpack a few months ago, and I now find it a bit suffocating and slow.