ORBX Global products, if you're willing to spend a lot of money. Global Base is a worldwide texture replacement system, but the package also changes the sim's terrain texturing architecture to improve how the textures align. Base might be enough to satisfy you; however it is designed to be enhanced by ORBX Global Vector and Global Landclass products.

There are also ORBX regions that are 'all in one' coverage for a limited geographic area. Check the ORBX website for demos.

For FSX, I went back to an older terrain texture replacement system called Ground Environment X (GEX) because it has less impact on memory and hard drive space. GEX can be further enhanced with the Ultimate Terrain X (UTX) line of products.

There are photoscenery products, both commercial and freeware. Photoscenery has its disadvantages though, including blurry down low. I think they also eliminate autogen objects.

Thank you