well, after a certain amount of population, specialists can give 3, 4 or 5 resources, so it can get even better than tiles.
The thing about this game, is that you can build really really amazing cities, and whilst tiles DO matter, your strategy and investment in cities matter even more! Which kind of makes sense.
In real life, london's terrain isn't much different that manchester, or washington isn't too different to NY or even some other village in grassland. The thing about those great cities is the infrastructure and population - this is emulated in Civ Rev.
Civ4 made a lot of advancements in making distinctions between a civ who chooses to have a few high quality cities and one which expands a lot.
In civ rev, to have a good city, its generally best to have some other cities feed it settlers - and at this point the land around the cities stops mattering so much!