Air China on the 777 should have the same seats that UA has on the 787 in business class and the same seats LH has on the A380. On the Airbus it will be a different, but I feel wider and more comfortable, lie flat seat.
Service will be better than UA or LH. Food will be OK but not great and entertainment will not be very good.
All in all I'd rather take CA than UA or LH.