I have a detached garage with an apartment above it. I have a linksys wireless g router all the way on the opposite side of the house, meaning the wireless signal doesn't reach out there. I want to have an internet solution without having to buy another modem and that is gaming friendly (ie won't cause excessive latency, good dl speeds, etc.).
I guess it depends how hardcore your gaming is. Some wireless router manufacturers are starting to do the gaming thing. For example Netgear advertised the WNDR3700 as the ultimate gaming router.
I wouldn't disagree with Wayne that a gigabit ethernet wired connection all the way is the best solution, but if you don't want wires through your house or to use your electric supply, then a full wireless N network all the way may still cut it. Though I do come back to my opening caveat - if you've got a monster gaming rig with a £500 video card, bigfoot networking, etc then you'll want the Gigabit wired solution.