I think they are 3 good ones.
My experiences are only on European flights:
KLM is the most reliable in terms of service: good standard (not great but always the same, that is good...), AirFrance and Alitalia can go from the super top to the lower bottom, accordingly to the crew, the day and the weather
This is true expecially for Alitalia: You can't find anything better of a business class seat in an almost empty MD 80 with a young crew, but the next time you can be totally ignored in a superbusy A321 for a couple of hours by a rather unfriendly crew.
In terms of hubs, Malpensa is weak. It is new and spacious but ground services are still too often rather crap. Not always a fault of Alitalia: try to wait 20 minutes in front of the only policeman at immigration with a 747 full of Japanees tourists in front of you. Alitalia lounge at Malpensa is possibly the worst lounge in the world I have been into.
CDG is nice, but do not even dare to plan a connection between CDG 1 and 2 with less than 2 hours in the middle. It is just not relaxing, most of my colleagues and myself just ask our travel agent to avoid connections in CDG if another option is available. The architecture of the terminals is great, but not at all my favourite in terms of practicity.
Amsterdam is a great airport. Better with roller skates on....