Well, I have absolutely no experience with American carriers, so I can't comment on them, but I have flown on several European and Domestic carriers numerous times, and I will say that, IMHO, Air Canada is the most disgraceful 'Full-Service' carrier ever. Poor service, bitchy personnel, terrible amenities, terrrible food. I'm talking about food poisoning, inconsiderate and rude flight attendants, numerous delays, and Young Frankenstein as the In-flight movie on a Toronto-UK route, and broken seats on more than one flight. I'd rather fly Air Transat or Zoom than ever set foot on another Air Canada plane, and all this nonsense about supporting our 'National' carrier doesn't wash. Just like every other poorly-run Corporation in Canada they just want us taxpayers to bail them out for gross fiscal mismanagement. Of the European carriers I strongly support KLM with their cheerful, friendly (and I will add, VERY attractive) flight attendants, excellent food, tremendous beer selection, numerous choices of Inflight entertainment, etc. If flying to Amsterdam and catching a connecting flight to my usual destinations didn't add a couple of hours to my travel time I'd fly them all the time. I've also had excellent flights with BA and Air France, and the food on an Air India flight was good, as long as you enjoy curries, which I definitely do.
Cheers