I think Compressor 2 does a pretty decent job with MPEG-2, especially compared to the last version. But, if you need more control over the bitrate, you may want to look in to either the MainConcept encoder or Digigami MegePEG.X. If the source image is the problem and needs to be heavily filtered and preprocessed, then I would look at Popwire Compression Master.
In my recent testing, I've found some pretty significant bugs in Main Concept when doing 16:9 "24p" files for DVD. And Digigami's doesn't offer a data rate controlled 2-pass VBR mode. Compressor 2 looks great overall in terms of quality, with the exception of long sequences of static images in VBR mode. These appear to get starved for bits due to the lack of a minimum data rate setting.
My favorite MPEG-2 encoder overall is ProCoder/Carbon. Its only significant limitation is that it doesn't handle I-frame insertion perfectly yet (they're working on this).