In general, from my own experience, I would say that my Japanese cars have been a bit more reliable than my European cars.
The fit and finish of both types have been excellent, though I must say that the Euro cars have used nicer overall materials. Compare it to the domestic trash I have experienced and the difference is drastic!
I must have good car karma, but I have never experienced a catastrophic failure in my Japanese or European cars that has left me stranded. What I have experienced tend to be very minor issues. A few more squeaks in the European cars, which were eventually resolved, and a few more electronic bugs that were eventually resolved as well, again nothing major. For me the driving enjoyment, prestige, style, that the European cars give back is worth the minor hassles that may accompany them.
The main advantage the Japanese cars have is that their luxury cars are based off of more common vehicle types. Like it or not this is a true statement: Examples: The TL is an US Accord, the TSX is a Euro Accord, the RSX is a Civic, the ES330 is a Camry, the IS300 is a Japanese Altezza, Lexus SUV's are all US Toyotas, the G35 is a 350Z, the I35 was a Maxima, the G20 was a Sentra, etc. This ability to rebadge/remarket vehicles, specifically in the US market, (What can I say we are suckers in the US, we seem to fall for marketing consistently) gives you the ability to share major components and production facilities which will in turn keep costs down. Really it is pretty simple, to be unique and not have to share components with "lower" line vehicles you will have to pay up.