I's say the worlds best 4 door classic is the 1971(XY) Ford Falcon GTHO Phase III, which in its day was the fastest 4 door production car in the world, with its 7000+ RPM fully worked balanced/blueprinted factory Holley 740cfm equiped 351 Cleveland V8 racing engine, 'Top Loader' 4 speed manual & Detroit Locker 9" rear end it could do the 1/4 mile in 14 seconds & had a top speed of over 160 MPH. It was a Homogulation Special for Production Touring Car racing, which meant they had to make a production run of at least 200 cars(or was it 1500, I forget which), for all the mods to be race legal
As far as all 4-doors are concerned I'll also go with the Audi S8, you can't beat an alloy space frame 'n alloy body, a 40 (5 valves per cylinder) valve quadcam V8 & quattro AWD.