Seems to me how you define big. If it is influence, I'd give it to Japan. If you include handhelds Id'd give it to Japan. But if you are looking at home consoles and a healthy console ecosystem then the UK certainly wins.
As a side note, it is common knowledge that Germany is PC-centric, but why? Maybe I should move.
XBL: WiiVault Wii: PM me PSN: WiiVault
PC: AMD Athlon II Quadcore 635 (OC to 4.0ghz) , ATI Radeon 5770 1GB (x2)
MacBook Pro C2D 2.8ghz, 9600m GT 512 iMac: C2D 2.0, X2600XT 256