Got a question about bandwidth use in online games

Say you have a port-forwarded next-gen console and…say a 10mbps connection. When playing online, will the console (if you aren’t doing anything else like web browsing on a pc at the same time) monopolize that entire 10mbps, or will it just use…however much of the connection that consoles use for online play? And does it depend on how graphics-intensive the game itself is, and/or how many other players are gaming with you?

I’m not asking something like “how close to an internet cap would a couple hours of gaming put me?”, I just want to know what kinda broadband connection (10? 15? 40?) I should be shopping for when I switch providers and move up from 1.3mbps next month.