Anyone live in Las Vegas?
If city success was dependent on its location alone, there'd be no Las Vegas.
City location matters massively in the early start of the game. You don't just "get" food after all.
But let's face it, later on in 4X games, it becomes largely irrelevant just like it should except in times of war when sieges should matter.
The funny thing about the "realism" argument is that cities being dependent on local food alone makes for a very unrealistic game because it makes it very hard to starve a city into submission because each city is self-sustaining.
In Elemental, players end up encouraged to build cities based on their strategic or economic value rather than their food value (except early on where those first cities better have a lot of food nearby). But what happens to those cities when they're cut off from that global food supply? In Elemental, the ability to siege a city -- and I mean REALLY lay siege to a city finally becomes a reality.
As someone whose hobby is history, the sieges of Leningrad (not Stalingrad), Sherman's march to the sea, the siege of Athens, etc. all give the same compelling story.
And yet, our strategy games typically don't give us the opportunity to do this because we don't have global food -- cities are self sustaining.
In http://en.wikipedia.org/wiki/Peloponnesian_War Athens was NOT self-sustaining. And during times of peace, it didn't need to. Food "magically" got to it from the rest of the Greek city states. But during war, suddenly it was reliant on its local supplies and was starved.
The history of warfare has a great many examples of winning through sieges. But TBS games have tended not to be able to demonstrate this because it requires food to be global in order to encourage players to build cities based on other factors other than food.