Be my guest.
I havent 'experienced' all the different variations.
In general, if this is a once in a lifetime experience, I think SQ is definitely the grandest, followed by LH and LX. If UA just stay at home.
For someone thats in the air once a week, I don't think theres a definitive best between LH/LX/SQ. It comes down to personal taste and mood, although generally the most important factor is schedule. I personally all else equal would take, LX>LH>SQ, unless it was a really long flight in which case SQ>LH>LX. Really depends on my mood.
Also, connections are a big factor. Connecting in FRA is a pain, but the FCT is awesome. So depends if one has enough time to relax there, in which case its a plus, or if one doesnt, in which case FRA is a minus. ZRH and SIN are both from the nicest and most efficient airports in the world, but the FCL in both are nothing to write home about (although you should definitely write to UA about them).