Press and hold the power button until it restarts. Might take as long as 20 seconds, but that works with pretty much any phone with a fixed battery.
However, I don't think that will cancel a hard reset, unless for some reason the recovery locked-up before the reset started. If you've started a factory reset it will have done it (and if it has only partially done it and you interrupt it then you'll almost certainly need to complete it for the phone to be usable!). But as it's now more than an hour later either it has done it by now or it's hung up somewhere, so you should force a reboot anyway and go from there.