I'd vote for the Buick LeSabre because I prefer front wheel drive. The LeSabre I'm driving now is at 130K and is as near perfect as any car I've owned. I took it on two 1000+ mile trips last summer, and I'd go again tomorrow if I needed to.
I like the Crown Vic/Mercury Grand Marquis too. If I were buying one (and I have) I'd rather have the Merc as they are never acused of ever being an ex cop car. Crown Vics get that accusation all the time, whether they have been or not.
I've seen SEVERAL of all the above with over 300K miles.
I've not had a Lincoln Town Car in several years, but recall that the '92 I had was plagued by electrical gremlins, and had air bag suspension issues as previously noted. I think that was fairly common on those cars.