Wow, what a hard question. I'd rate them all about equally.
European games normally play to my sensibilities better. Things like LittleBigPlanet & Fable this generation, things like Theme Hospital & MediEvil in generations gone past. Just have a distinctly British feel to them and I really love that.
We're also king of racing games, in my opinion. WipEout, Burnout, Motorstorm, Blur, PGR to name but a few.
I like Japan, mainly for the JRPG's - PS1 era Final Fantasy games, Wild ARMs, Valkyria Chronicles. Kingdom Hearts etc. There haven't been a great deal of these that I've enjoyed this gen though, compared to previous ones (perhaps that's because I missed out on handheld gaming).
Japan often get platformers right too - Ape Escape, 3D Mario, some Sonic games - but again, it's been a fairly quiet one for that this generation. Metal Gear Solid is the anomaly of a Japanese shooter that I really enjoy.
USA gets a lot right. The 3D era platformers - Spyro, Crash, Jak, Ratchet, Sly are some of my favourite games of all time.
There's always gems that appear in other genres too - Infamous, Uncharted, Portal, The Sims etc. all get so much right. But there's many big name IP's from the USA that I find less enjoyable.
I would have trouble picking just one region. I voted Europe because traditionally that's always been my favourite region for games, but it's been a quiet one this gen. Japan has been quiet for me too, although like I say - that may be because I missed out on handhelds, which I'll be correcting soon when I play PSP games on my Vita. USA is hit and miss - some of my favourite games ever, but a lot of over-rated stuff.







