As TB says though, they are hard to beat, which is why Im reluctant to change mine for something else.
That's the crux of the matter.  There is *NOTHING*, even now, that can match it.  I agree with Rangie that a FFRR surpasses it on comfort, but a FFRR is inconvenient in old 1960s NCP multistoreys, or my driveway.  Its well know I have an itch for a FFRR, but simply don't have the room after repeatedly borrowing one from our resident used car dealer.
I'm lucky in that I have some friends that do a bit of wheeler dealer'ing with german marques, so I get to have goes in some 5yr old 5/7 series, E class, A8 etc.  One bro has had a couple of spankers S classes (though we don't mention the current one, which is parked up unloved/unused and he pays full whack for it but gets a crap CLS in return 

 - that'll teach him not to listen).  I obviously went down the X351 XJ route because it was better than the rivals for me.
But if you want a non 4x4, or lack the room for something like a FFRR, there is nothing really that matches the Omega, certainly in the sub £40k 2nd hand market.  Yes, the technology onboard is a bit dated with no fancy touchscreen carplay Netflix streaming wank.  But I find it incredible that a 17yr old car, essentially a 30yr old facelift or a 40yr old design, holds its own against any other saloon/estate out there.  But it does. And wins.