OK... Let's see.....
The Beatles --- They're out on so many discs that you're really going to have to look at each disc to see where your minimal "repeat Factor" will lie. But, as a start, you can check" Zoom" Discs... I believe they have 3 or 4 full CDGs devoted to The Beatles (including some rare songs that nobody else ever released on CDG). I don't remember now, but I think "Amerising" (or is it Amerasing?) has a full Beatles CDGs. Other than that, other makers have you'll find mostly a song or 2 here and there that are mixed on other manufacturers discs. All-in-all, there's about 150 Beatles songs out there on CDG.
The Eagles - Again, "Zoom" has an Eagles disc as well as a Don Henly disc. IMO, don't waste your time looking for that ever so elusive "Sound Choice" 8125 (which was pulled from the market about 1 year after it was released, because Don Henley did not want his stuff released to the Karaoke world). There is a "BackStage Karaoke" CDG that has 15 songs... a lot of people say that the disc sucks, but I personally don't believe so.
Classic stuff - You'll find tons of classics... some on single artist discs and some that are just mixed on a 50's or 60's or 70's, etc... disc. You can start with "Pocket Songs." After that, check out the sale that's going on right now with Dow Wop Karaoke at
www.doowop.com and their new website,
www.doowopmushicshop.com. They are having a $6 sale on remaining "Pioneer" CDGs (as well as a few others, but I strongly recommend that you add "Pioneer" to your library while you can... these are out of print/discontinued). For more classics, you can continue your search with "Sound Choice" (but it will be as I described above... 1 or 2 songs here and there all mixed together on multiple discs).
For current stuff, I recommend "Pop Hits Monthly" (Pop).