Try x264 . I get perfect results in detail and color.
Install MeGUI
sourceforge.net/projects/megui/
Get all of the updates, you will get some MeGUI components. Add a shortcut to your Desktop.
FIRST you'll need to create a script for every file you convert.
Go to Tools > AVS Script Creator.
Under Input click ... in Video Input. Choose a video file. Then there will be some windows, I do not remember what they are about, but I think you will understand what to do.
Click Save at the bottom of the AviSynth script creator window.
SECOND choose video output in the main window
THIRD In Encoder section press Config.
Enable Show Advanced Settings. Encoding Mode Automated 3pass, Bitrate 1000 (works fine for me, but you choose whatever you want), Preset Slower (Very Slow), AVC Profile High, AVC Level 4 for 1080p (choose Level 3.2 for 720p, more info: http://en.wikipedia.org/wiki/H.264/MPEG-4_AVC#Levels).
Save this preset. It helps in the future. Click OK.
FOURTH select MP4 in File format.
FIFTH Click AutoEncode
I hope it will help you with H.264
If you have a lot of files to encode you can use AviSynth Batch Scripter to create script for every file.