My vote goes to the Sheraton Grande Sukhumvit.
OK, a few stops with the skytrain to Asok, but then it's directly connected to the station, no need to even go to the street level.
I find choice and quality of the food unbeatable. Just about everything seems as fresh, colorful and tasteful as you can imagine.
Service is very friendly and efficient, sometimes even a bit too efficient.
The SGS breakfast buffet is one of the reasons why I still consider switching an upcoming reservation from the new shiny Sivatel to the slightly dated SGS.
Cannot comment on the Four Seasons or Plaza Athenee, but I heard not too good comments on the Intercontinetnal.