Why don't you post some of your work and we can talk about how to make them more realistic?
It's perfectly possible to create realistic characters with Blender, you can head over to blenderartists.org and see some truly amazing works. Making them work for real time and game use is just a question of optimizing where you bake ambient occlusion lighting, normal maps and simplify mesh topology.
But the biggest issue of course is to have the skill needed to shape realistic human characters and make clothing look plausible. Even more skill is needed for rigging and animating proper looking organic animations so your characters don't look like robots defying gravity and other laws of physics. Such skillset is not owned by many individual people and bigger game studios have dedicated artists working for each of the areas to ensure maximum proficiency and best overall results.