I run in to this with standard in-game captures. Some look fine as is, others not so fine. The not-so-fine shots get manipulated in PAINT.NET (and sometimes GIMP for more complicated corrections). PAINT's manual "level" control (not the automatic one, which produces horrid results with Oblivion captures) works wonders with most Oblivion images, restoring them to what I recall seeing on-screen during game-play. Since I invariably reduce image size to conserve storage space I also use PAINT to slightly sharpen the now shrunk views, as the reducing process tends to blur them. (I believe PhotoBucket automatically reduces images over certain size, but I prefer to keep control of the end result.)
-Decrepit-
-Decrepit-
And I run into quality issues with unretouched images with Skyrim, the initial jpg never looks as good as the ingame image...