This category is such competitive one as many models are available today & the engines choices are wide:
Take Merc for instance beginning with 4 cyl unit(E 200)and going up to V8 unit(E500).
Few years back it was most dominated by BMW & Mercedes(talking on the world scale).But every manufacturer today has entered this category hoping to increase profits.
This category includes:
5ser,E-class,S-type,A6...and many more.
To choose between these cars is getting harder every day....
Of course there is a lot more but these,I think, are the main players.