Honestly, my favorite spot is the Sheraton Four Points. You would be one block away from the Magnificent Mile (Michigan Avenue), and two blocks away from one of the Rosebud restaurants, as well as the best pizza in Chicago - Giordano's. There is an EL stop within blocks, and you can get to Wrigley in 15 minutes.
The cost is average for Chicago (for a nicer hotel): $195 - $245 per night (but if you look you can find some savings). Check it out here:
http://www.starwoodhotels.com/fourpoints/property/overview/index.html?propertyID=1592
I've also found great deals at the Millenium Knickerbocker, which is in the same general area.
If you want to save some $$s and still be on Michigan Avenue (although a little more South, but still walkable to Miracle Mile) check out the Congress Hotel. You can usually get a great deal on an older hotel, that is very clean and in a good location.
Hope this helps. We travel to Chicago often and stay in a variety of hotels -- Congress to the W -- if you need any info, let me know....
Oh, and if you are driving -- count on $30 a night for parking at most hotels....