Rainbow because it managed to release all the monsters from Barom-1's show in only a few years, Elegab for its unique universe, Yamomark for being so classical & modern at the same time & Zollmen for their ability to twist kaiju classics in an awesome way.
Over the years I've had many toys from many lines come in and out of my collection, but I always go back to SB..classic sculpts and amazing colorways. I never get tired of looking at them! SB4L!!!