When I build models I try to go for the lowest poly count that I can squeeze out of it and I use normal maps to fill in the detail. Also there are also a lot of source code examples for implementing other techniques for enhancing detail such as parallax mapping, relief mapping, cone-step mapping, etc...
These methods alter a models texture map coordinates to simulate how a raised surface will travel farther along an arc than a lower surface would. A surface further from the pivot travels a greater distance, to achieve this effect, parallax mapping moves the texture map coordinates further where the height map is "higher".
This technology even runs on mobile devices very well under OpenGL ES 2.0. With all the open source available it's pretty much in the hands of everyone now.
If the game is set up to do this then you really only have to concern yourself with the silhouette of the model since techniques that use textures to enhance a model tend to only break down at the model's edges where the surface angle is steep.
You could also make multiple versions of the same model at various levels of detail,
In layer 1, you could have the lowest resolution model,
In layer 2, a medium detail model,
In layer 3, a model that is a bit excessive.
This technique will give you options for different requirements that people may have, and it will also give you an edge with games that can implement LOD.
The only real issue here would be keeping the texture map coordinates synced up between the various levels of detail, but Blender and xNormal both can do a pretty good job of projecting the surface normals of a high poly model onto the low poly model even though the high poly doesn't have texCoords assigned.
Maybe the modeling program you prefer to use also has this feature. In Blender it's activated using the "Selected to Active" checkbox found in the "bake" section.
Even if you don't use Blender for modeling you could still use it just for this feature since it's free.
If you really want to pack in the most detail possible than you really should consider mastering the art of "modeling" normal maps as well as height maps. They tend to work very well since texture map detail is not subject to aliasing in the same the way real geometry is.
Normal maps also tend to smooth out aliasing problems on real geometry at many view angles. Just not along the model silhouette.