Strange question... How can you describe the "best" airline. Perhaps a better question would be: "What is your favourite European airline?"
As a Belgian I would say SN Brussels Airlines because I loved flying with them. But you should have flown all airlines to judge them.
from my recent experiences - LH Cityline and dba and SNBA is very fine, too, but my last SN Brussels experience is dated october 2003 and - LX last weekend was a nightmare (but not at all LX fault, maybe I will write a trip rep but no time yet).
Personally, first SNBA, due to the belgian story and the very good service (specially in business!) and second LH. I should place LX as third and IB at the last position.
Due to no experience in LCC, i can't give comments about those companies
I would say Martinair since they still offer a good service for very acceptable prices.
They are reliable and build up a good name but I must admit I do hear exactly the same experiences from people that flew with SN.
For Low Cost I still sayEasyjet, too bad they stopped their AMS-BCN service, they have to start a route to Spain again from AMS!
Of the European airlines, I've flown BA, Lufthansa and Austrian. Of the three, I liked the attitude of the Austrian staff the best and they definitely had the best meals. They all have a long way to go before they come close to Singapore, though.