Honestly, nothing beats direct non-stop flight in a decent business class. If you can afford it, Air France in business class would be my preference. It is a good business class product.

Other decent options are Lufthansa through FRA or MUC (would recommend MUC), OS via VIE, LX via ZRH. KLM through AMS also works well.
SAS through ARN is a fantastic long haul product but the European leg is pretty poor.

I’d avoid LHR and the American carriers.