Good discussion. Asking what the "best" games are is a big like asking who the best Beatle is.
Most revenue: The games that have historically made the most are MMO strategy titles, stats heavy and graphics-light. Ones like Evony and Travian were juggernauts in their day. Even now, you'd be surprised how much cash these crusty things make. (Their modern day equivalent is Game of War and Kabam's mobile games).
And of course real money casino games rake in cash, but are not legal in many places.
Most fun: Tough to quantify, but Kongregate or Addicting Game's most popular lists are good proxies. Usually very short, wacky "snack games."
But I agree that HTML5 is really the only viable tech these days. Here's a blog post going into more detail if you are interested:
We've built a bunch of titles over the past few years and with some work native-level quality is definitely now possible, for casual games at least.