I've only stayed in the Hilton on Michigan Avenue but it's reasonably priced, huge and within walking distance from a lot. The bus tour (which I take in every city I visit) stops right outside too. They also have a cheap shuttle to the airport and it looks out over lake Michigan.
Have stayed in Chicago numerous times, always in the Sheraton in central downtown.
Very nice hotel in good location and well priced.
It's just a few minutes walk to Michigan Avenue.
The Hyatt and Hard Rock Hotel are others in the general area.
IMO the Hilton is dated. Our room stank and South Michigan Avenue is a bit out of the way. North Michigan and the surrounding blocks are the most central and good deals can be got on hotwire and priceline. My opinions on the various city centre hotels I've stayed in are posted in the thread I've linked to.
Would you consider staying in a self catering apartment rather than a hotel? We did this in October, had a lovely place about 50m off N. Michigan Ave near Water Tower Place, would highly recommend it! If you'd like details I can PM you, for 4 people it was approx €350 each for 8 nights.