You could not escape Three Dog Night at the American school I went to. I never had issues with them, they certainly had a knack of elevating most of the material they covered, kind of like Manfred Mann's Earth Band whose covers always sounded better to me than the originals. And I did own "Cyan" as an album and only a few years ago bought a bunch of their CDs.
And if Joy to the World doesn't put you in an ebullient mood a couple of seconds into the intro, you have no heart!
I saw Chicago a year or two ago, not expecting much, I only came for Blood, Sweat & Tears, their opening act. Contrary to all expectations, Chicago gave a firework of a great show of their material old and new(ish), hugely varied, but without any seams showing, I was very entertained and the musicianship was top notch. Nice bass playing (and singing) by Jason Scheff too. I'd go see them again anytime.