I guess 'downtown' is a pretty generic term in a big city. There are so many areas of interest, I'd suggest figuring out an area to focus on , then pick a hotel near that. Shopping? Magnificent Mile. Museums? Museum campus. Ethnic? There's Greek town, Italian village, Ukrainian village. Maybe pick a restaurant or two you'd wanted to try and stay near there. Or just pick a place close to the lake south of Illinois and north of Roosevelt and you can get anywhere you want using public transportation. You can just plan a walk around Millennium Park to look at The Bean and catch a free concert. Go on the architectural boat tour on the Speed Dog along the Chicago River. Lots to do, I don't think you can go wrong! I don't know hotels, since I don't stay in them while in Chicago, sorry I can't help with that.