I bet it's a little more than 5MB per hour, but still not a whole lot of data.
Like it has been mentioned, bandwidth, or the amount of bits transferred, isn't the issue. It's the latency/ping, or the speed at which bits transfer, which can cause problems.
Games that don't have a lot of synchronization will have a lower demand on ping. Racing games are an example of this. You basically have to know where the opponents are, and that's it. Whereas games like Red Dead Redemption, you have to know where they are, what gun they're using, their current animation, where they're looking, etc. Even if it isn't a first-person shooter, it still has a lot of data to sync with all those that are playing.
I would say that lower demanding games are tolerable up until 250-350ms ping, where as high demand games start to struggle at the 120-200ms mark.
Edit: I know on the iPhone you can download a SpeedTest
app which will tell you your ping and bandwidth. There must be similar apps out there for Droids and Windows phones.