Ground is incredibly difficult to get right. You usually have to cover a very large area, and you can't spend more than 3-4 texture layers on the ground. There are many tricks... use tiled textures, a large lightmap, a heavily tiled detail map, and vertex colors to add color and pattern variation, alpha blending to transition between different types of ground etc. etc. But there's still a limit on how much tiling you can have before it becomes too obvious, and how many different textures you can use and at what resolution.
So you can either resort to less acceptable tricks like limiting the visibility of the scenery through the level design, or limiting camera motion, especially zooming in/out - or you have to accept that the player can get into a position where the ground does not look good.
Also, good looking ground would require enourmous amounts of geometry, the surface should be bumpy, you'll need small rocks and big rocks, and so on... No current GPU has enough power to do this, and what's even more important, such fidelity takes a hideous amount of work.
We usually cheat in CG: our concept artists paint 2D projected textures for every major camera angle, sometimes using cameras with huge field of view for shots that have a lot of camera movement. This way a single texture will have a 1:1 or better texel to pixel mapping - but this method relies on knowing and optimizing every shot and is not adaptable for an interactive enviroment.
This is the same scene from two different camera angles, and the ground is a different painting basically in both shots:
One
Two
Pixar had to do detailed ground in Bug's life first and they've relied on procedurals, but they aren't bothered if the results are cartoon-like. They've made some nice progress in the past years and Cars is quite realistic, but I have no idea how many tools and how much processing time it took to build those enviroments. These methods will probably not be feasible for games for a long time either.
I think Carmack's MegaTexture may be a solution, but Quake Wars screenshots seemd to show that they've been aiming to make the ground look good from medium distances, and not from close-ups either. And it's terrain is quite low poly, too. I wonder how the next id game will look like.
And by the way, there have been games with good looking ground in close-ups, like the original Halo on Xbox. But it did not look that good from a distance, when you've been able to use the Banshee to fly around.
