I'm surprised people prefer US-based airlines. We are so far removed from the days of Pan Am, TWA, and Northwest -- US airlines that specialized in quality international service. If you like a 30-inch seat pitch and 17-inch seat width in economy (777s have been refitted with 10 seats across instead of 9), the possibility of crossing the Atlantic on 767 (or, occasionally, on a narrow-body 757 if flying from the east coast), limited food and beverage options, etc., then US carriers are perfect.
Delta's effort to improve transatlantic coach is like the Doublethink "increase" in the chocolate ration (from 25 down to 20 grams) in Orwell's "Nineteen Eighty-Four". Economy passengers had hot towels and a choice of meals 30 years ago! The "welcome drink" in coach upon reaching cruising altitude actually allows a reduction in staffing: serving everyone a small portion of the same drink requires fewer flight attendant duty hours than running an initial beverage service with full, individual choice.
I choose major foreign carriers whenever possible. Lufthansa is my favorite, with Air France a close second.
Air Canada is a hidden gem, offering competitive US-Europe fares via Toronto, Montreal, Vancouver, and occasionally Calgary, as well. Their service is closer to European standards, and many of their fares allow a free stopover in Canada.
For those who live in small towns, keep in mind that the major European carriers all have alliances with US carriers for your domestic connection. Even though both partners might offer the same itinerary at the same fare, try to buy your ticket from the partner that operates the transatlantic flights. This lets you manage the part of your itinerary that matters, with less hassle. For example, it's easier to select seats, special meals, etc. on a Lufthansa-operated flight (seats if seat selection is possible with your fare) when the ticket is issued by Lufthansa than when it is issued by United with a codeshare Lufthansa flight number. Ditto for making changes once you are in Europe.