Hunter x Hunter
You could have it be 50 years after, but you could also have it be before too, and it'd get rid of the ants that way.
Systemwise, you need something that can handle all the absurd, off-the-wall powers, so something like GURPS if you want extra crunch, something like FATE if you want little to no crunch, or something meant to handle superheroes like M&M.
A flaw in HxH is that there are far too many arcs that just wouldn't be fun. The gaming continent would be a little too meta, the initiation too railroadey, the battle tower too much of a drag with too little RP... The game would do well to focus on the other things we're told hunters do instead of what we're shown most of the time.
Oddly, the ant arc is part of the kind of stuff you'd want doing, just without the stupidly overpowered ants or needing to have most of the overly powerful npcs drop by to save the day.