If you gave everyone here the task to pick the ten greatest, I suspect there would be lots of overlap, and a few stragglers. Same if you said to pick the top twenty or twenty-five. We have a good idea of what are the greats, the near greats and the onlookers. When you get to fifty I think you run out of greats and start to look for shows to fill out the last of your ballot. The fact that there was a lot of clumping at the top shows me that as a group we're of like mind and know what great means more than some silly TV network or magazine.
My last ten were: Supermarket Sweep, Hot Streak, Hollywood Showdown, Dirty Rotten Cheater, Talk About, Chopped, Late Night Liars, Remote Control, Million Dollar Mind Game and finally Estate of Panic, because by golly I just enjoy it. The point I'm making to allay the "well, I did thus and so, and here's why" is that of course this exercise isn't purely scholarly, there has to be some amount of opinion and feeling and personality that goes into it and that's what makes it fun.
To Mark's question: they weren't. $20k ended in 1980, $50k went a year-ish in 1981 and New $25k picked up in Fall 1982. $10k was also off the air for a month and a bit in 1974 when CBS cancelled it and ABC scooped it up.