With all due respect, have you been to the Vienna airport? It's on par with LaGuardia (worst in the US), if not worse.
Europe has some nice airports (Zurich, Copenhagen, Helsinki, Stockholm). These are largely smaller airports in smaller cities... just as many of the nicer US airports are in places like Sarasota, FL, or Seattle.
But plenty - like their US counterparts - were built in earlier eras and very expensive/difficult to renovate (look at Berlin's Brandenburg Airport debacle). So they remain either fully outdated (Berlin, Milan, Rome), or a hodgepodge of gross old facilities and some newer additions tacked on, similar to Logan, JFK, etc., etc. Most of Europe's bigger airports (Munich, Frankfurt, Dusseldorf, Amsterdam's Schiphol, Heathrow) and plenty of others (Geneva, Madrid, and Dublin (at least when I saw Dublin last 10 yrs ago)) are in that boat, IMO.
If you want to feel bad, go to Zurich's airport. But it's not that representative, even of Switzerland (the only other real airport in the country, in Geneva, is gross). Logan is on par with most, and a JFK is probably actually ahead of the Euro pack after its many recent renovations ... just don't let the horrendous roads leading in/out of JFK factor into the equation.