For the best ever color sets I would have to pick the Sony Trinitron, from the late 60's on till at least the early 90's they set the standard for picture quality that everyone else tried to match but really couldn't till the patent ran out on the Trinitron CRT.
I would single out their XBR line as particularly good.
Hard to argue with the Zenith B&W sets of the 60's, superb build quality, great pictures and frankly I don't think anyone was really trying to build a better B&W TV at that late date.
the little RCA 8" portables from 56-57 are also amazing sets, not so much for the picture quality which is average at best but from an engineering standpoint they are a work of art!
They are a transformer powered, well built, quality TV in a very small package for the time!
The competing General Electrics of the time are junk (but cute junk) by comparison. Obviously aimed at different market segments.
Worst color set, gee there are so many, GE made a particularly nasty set in the 60's, (not a roundie) it used the "KD" chassis as I recall. I actually fixed one up for my Grandmother in the 70's, poor thing must have gone half blind trying to watch that dim crappy thing.
The Predicta is certaintly a nightmare to work on at least, and the bad CRT's...
Someone will probably mention Muntz in this thread
I have no first-hand experience with them so I can't comment.