Very low quality gifs with ffmpeg ¿Its possible better quality?

Question

Hi all, Im using ffmpeg.exe to generate Gifs from video files. I use this code:

"C:\\ffmpeg\\ffmpeg.exe" -ss 455 -i "C:\\ffmpeg\\movie.avi" -pix_fmt rgb24 -r 0.05 -loop_output 0 -t 100 -s 720x400 -f gif "C:\\ffmpeg\\animation.gif"

But the quality is really bad, I found in the web similar cases: http://ffmpeg-users.933282.n4.nabble.com/Bad-quality-with-ffmpeg-s-GIF-encoder-td2329046.html#a2399722

There's possible generate gifs with a better quiality using ffmpeg? Thanks in advance.