Depends on the type of game. I could go as high as $100 US for a hugely expansive, open-world RPG (something bigger than we've yet seen, I mean)... but for arena shooters, spectacle fighters, linear RPGs, et cetera? $30, tops. Expansive, complex strategy games fall somewhere in the middle. $60 feels fair.
...to say nothing of corridor shooters. They'd have to pay me.
But then, I'm one of those people who bought Chrono Trigger full price on launch day as a half-employed teenager. $60 for big RPGs these days is a bargain in comparison.