The most rerun-abused classic right now is probably Greed, because of its short run. GSN still gives it two showings a week on the March 15 schedule, but I have to think a rest is coming sooner or later. Can't really say that Jeopardy or WoF look abused to me, because I watch them very sporadically on GSN. Whenever I catch an episode, it seems brand-new. I never watch H2 at all - Bergeron, Marshall, whoever. 100K Pyramid might be a little abused from my viewpoint, though I often catch shows that look new to me.
Which, of course, is the real point. Unless you lock in on a certain show and watch almost every ep religiously, it's hard to complain about rerun abuse. I might miss my guess, but if I sat down and watched GSN straight through from the end of the infomercials to the start of the left coast prime time repeat, at least 75% of the classics would be new eps for me...or certainly episodes that I couldn't remember seeing.
The Boden originals are a different matter, because I've seen virtually all of Lingo and most of Cram and RR...all fairly recently. So they do look a little rerun-frayed around the edges, though I can still enjoy them. If I ever dropped in on Friend or Foe, though, it would look pretty shiny. But I don't plan on doing that any time soon. I've seen enough of the backstabbing-fest.