What a shame to hear, but I have to say that Lufthansa vastly eclipsed my experiences with both KLM and Air France / Delta on my last few trips. We flew LH over Christmas, and the family in front of us was a young couple with apparently limited flying experience AND with a baby in a bassinet. The cabin crew did such a lovely job of talking them through both the normal and emergency procedures and really taking the time to ensure everyone--parents and baby and those nearby--was comfortable. The food service was efficient--no trays sitting there forever while you have to visit the restroom. My recent trip on AF last summer had numerous problems--none of them the fault of the airline (a medical on board, a birdstrike, and the climate crazies gluing themselves to the runway), but all of the rebookings were poorly handled and the poor service at CDG made the whole thing even worse. The North American connection was with Delta, and that whole mess plus the resultant baggage fiasco were absolutely AWFUL, leaving me hoping I wouldn't be wearing Walmart clothes to my grandfather's funeral and costing me precious time with family to deal with luggage during this time.
The Frankfurt airport is very German--efficient and not meant to be pretty. Boring concrete look, but you can get from A to B quickly and effectively. I find Amsterdam way more inviting for the most part but less secure and Paris absolutely awful--I will pay extra not to fly through CDG (fine for originating or terminating, awful for transfers). I once entered the Schengen in Amsterdam and through a freak of where staircases were ended up never even showing my passport. I have also been stuck in lines counting down until my flight or stuck in a US bound pre-check area with no food or water in AMS. I have never had any truly memorable experiences at FRA, either good or bad, and that is a solid recommendation in my book.
But like any recommendation, it is based on experience. Over the decades, we have found LH and FRA to be solid, KLM and AMS as well, AF and CDG awful, and BA and LHR perfectly fine until you have a tight connection. We hate United, but have flown with them a heckuva lot because of where we were living in the US. We have flown through other airports around Europe and think Munich is great, but those are the ones we have used most frequently. Pretty much every truly bad story we have somehow involved CDG.
