I would say SQ is the best product, but the service delivery is robotic and leaves a lot to be desired. CX have a good product and good service delivery. Emirates has a poor product in the air (3 x 4 x 3 in economy on the 777, no beds in Club), compensated for by excellent crew and ground facilities. KLM has a poor product, poor service delivery and lousy ground facilities.
Have flown BA LGW - IAH return on average once a fortnight since January (in Club). The service delivery is very consistent, and consistently better than at Heathrow. BA are let down by some very camp male cabin crew (their orientation doesn't bother me, their manner does). The long haul Club product needs a revamp.
Have only been down the slides once and BA did well!
Am now flying to Lagos, where BA and Virgin are head to head. Those who have tried Virgin (we are all well worn gold card holders) prefer it: it is the product they mention (seats, beds, food), not the cabin crew.