I think this is an interesting philosophical point. Should the man who built the theatre get more credit than the playwright? Should the engineers behind the modern tennis rackets get more credit than Roger Federer?

I think there must be a balance in between. The hardware contributions by America do not clinch the debate, but they do work heavily in favour of the USA. Then one has to take into account the software side. The US has also spawned a huge number of top-notch games and indeed crafted entire genres but I, personally, think Japan has done even more on the software side (yes, that includes taking into account the historical efforts of the USA). Where does that leave each nation in terms of overall contribution? It's a difficult one. I wouldn't discount sales completely, I think they are definitely a factor, but  one among many. Once again, they should not settle the matter.

If we're talking overall gaming:

USA (Atari, PCs, and all the major founding technologies that made gaming even possible. There is no greater innovator in gaming.)
Japan (Console contributions, great business models, NES which helped the US out of the crash of 83, arcade gaming in the post-Atari world)

Everything else is secondary, really. The UK and Canada have made great contributions in the areas of developers, but not as much for the actual machines.

USA then Japan; there is also Europe and Canada.  Including the PC market, the US has done a lot for gaming.

I Think in the world Asian countries are known for the gaming and developers are mostly from asian countries. But USA and UK are aslo developing. Because people think about to develop more games for the people who are crazy about gaming.

Dion
Free Satellite TV

well considering those r the 3 biggest markets for games then it makes sense for them to contribute the most. however, canada has made some realy good stuff, Ubisoft Montreal didnt they make assassins creed?

America as contributed the most. Not in the form of having the best polished games(MGS4, FF), but that they have contributed to more forms of games and do them well. Survival Horror, RPG(JRPG is based off "WRPG), shooters, sports, strategy, puzzle adventure(Kings Quest), QTE games (Don Bluths Dragons Lair). Without America contribution to the gaming genre the gaming landscape would be far more bare.

Japan is a master of polishing games and repeat that polish well at least manage to get more of them out more often. They however have also brought in platformers, brawlers and fighters. And pretty much are the best at those.

UK or really Europe doesn't come out with new games or polish games as much, but they take a game and do something different that makes it excellent or new.

I'm going to ignore the puzzle game category since all countries seem to have a good mind and developing these.

Clearly anyone with certain gaming preferences say God of War type of combat platformer or prefer the sub styles of the JRPG will choose Japan, people like me who prefer more interactive RPG styles will prefer America. But preference aside America is clearly the bigger contributor to the gaming industry.

Ok, I'm going to start annoying people now with my UK fanboyism, but how can you say the following games aren't new?:

Elite, Theme Park, Lemmings, Populous, Grand Theft Auto, Worms

or polished:

All of the above, Syndicate, Little Big Planet, Banjo Kazooie, Rome:Total War, Tomb Raider, Canon-Fodder, Golden-freaking-eye!

I mean, come on. Yes the USA and Japan are tops, but please don't just say "Europe" and then imply that the UK basically hasn't given much to gaming.

The Soviet Union, which single-handedly created the puzzle genre :P

Tetris is I think very underrated here.

Burnout is also from the UK (Criterion), as is Singstar and Eyetoy (Sony London), and. Football Manager. The UK definitely has the most hit series for the smallest population (the best population/hit game ratio).