Worst London - take your pick of the rest - all miles away, all pretty grim! Perhaps Luton worst of the lot?
I quite like Luton. Security queues never that bad (and a fiver or so to jump the queue if they are), a nice, vaulted roof terminal, most gates not too long a walk (other than the old terminal gates used by Ryanair and gate 19), very quick luggage delivery (no faffing about with belt systems, just drive it over on a flatbed Transit) and very soon a proper link to the station too. Also much more spacious since they built the "new bit" on the front.
Stansted is dross in my view. Slow to get through in both directions, slow baggage and a generally mucky, run down atmosphere. Also has the stupid feature that if you get off the transit at the wrong stop you have to go through arrivals, get a new boarding pass and through security afresh - this caused some friends to miss a flight a while back (yes, actually friends, not me!) - you also can't go back to the main hall if your flight turns out to be delayed. And as if it wasn't bad enough if you're using it you're almost certainly flying with Ryanair.
Gatwick is a very slow airport to get through indeed, though is at least in a decent state of repair. Very similar to what Heathrow was before the new terminals.
LCY I think is now utterly terrible. It was good when it had 10 gates and was mostly Fokker 50s and Dash 8s, and the terminal had a "whole thing is the business class lounge" feel to it, perhaps like how flying might have been in the 60s. It can't even remotely cope with the extra gates and larger aircraft and direly needs a completely new terminal. I would avoid it these days, even if take-offs and landings on the short runway are quite fun (though not for those with the fear of flying).
Best Switzerland - Zurich - the epitomy of Switzerland!
Yep, it's excellent, it even *looks* Swiss.
Worst Switzerland - Geneva - probably has just out-grown the space available, but definitely in need of a re-think
Geneva is certainly not what you'd expect in CH, but Zuerich very much is. But it's not a bad airport, as a former regular I quite like it, including its quirks, and it's fairly quick to get through. The security queues at peak time (winter) were a sight to behold, though, and no "pay a fiver to jump the queue" option, only for those flying business/with status on some (but not all) airlines. They are also underprepared for snow, which is amusing given that they get it for several months a year.
Intentionally, one hopes.
I've done a Vancouver seaplane "tour" - great fun!
