I have lived in Chicago for 12 years, and while I love visitors, I usually loathe what they want to drag me to do downtown. I'd much rather show them a new neighborhood, which is nearly always more interesting and less expensive than anything downtown.
The architectural boat tour is the exception. It sounds boring, and I often have to say something like, "I know it sounds nerdy, and I need you to trust me on this."
The lake & river tour usually starts by going south on the river, with gorgeous views and fun explanations of the wild architectural innovations that occurred in Chicago's history, resulting in a gorgeous downtown full of unique structures. It's so relaxing.
Plus, there's a bar.
Then, out on the lake, the wind whips (usually pleasantly), and you get the full view of the skyline, a view you can't get from anywhere but well out in the lake. There are a few tidbits the guide shares out there, but it's mostly just a comfortable cruise with incredible views.
I highly recommend checking the weather and avoiding the tour just before sunset, as from the lake, the buildings will mostly be in silhouette, dimming the many colors of the skyline.
For locals and tourists, I highly recommend spending an hour and a half loving on the city with one of these tours!