I miss the audience murmur then quick hush at the top of "Jeopardy!" That opening was better all around. The music (such as it was) said exciting competition, rather than the current music, "if you're under 60 you should be doing something else." The exploding globe would look dated now but was cool. Contestants walking in made a better visual than them being in place already.
This. I loved the opening with the introduction to the main theme and the contestants walking in. Also, by the time I was old enough to remember, they weren't using the first few bars of the opening outside of tournament finals, which always seemed to add to the drama when it was played in full.
I miss physical game boards. I can understand why Wheel dropped theirs (and the current incarnations of Feud and J! never had them at all), but you do lose a little something when your entire set consists of 40 monitors, one host lectern, a couple sliding glass doors, and a bunch of abstract shapes (as is the case with Jeopardy at the moment.)
Also, seeing set pieces rotate, fly in, etc. These days, teleportation via jump cut seems to be the norm.
Live-to-tape, at least in part. Partly because of my previous paragraph, partly for the little bit of behind-the-scenes glimpses that we could see because it wasn't worth it to stop down and reshoot. I don't think that any modern show would leave in the Super Password board's frequent malfunctions or even the "we'll check the tape and tell you if you won after the break" moments that Pyramid occasionally had after a close call in the Winner's Circle. However, I don't miss the breakneck final rounds or the looooong stretches that were occasionally necessary to bring a show in on time.