To answer the OP's question, the alternate routes are not that great. A lot of the traffic stems from a bottleneck which was created when they redid the I-90/94 split in the city a number of years ago. They messed up the southbound flow on 94 to improve the northbound flow. This makes I-94 (the Edens Expressway) a real mess during the reverse commute, and means that more people take I-294.

The alternatve isn't great - unless you are a native and can handle the risk of getting lost on side streets, there's only really one decent alternative - get off at either Willow or Golf, go west to US 45 and go south to US 12 south, then don't get back on 190 but take the back way into the airport rental car facility by turning right at the first stop light after IL 72. This approach will take you through downtown Des Plaines. I don't think you'd save any real time, but it might be less frustrating.

If you're daring, you might try Golf Road east to Potter south to Busse east to Dee south to Devon west to River south to 190 west into the airport. Smaller streets, less truck traffic, but probably worse traffic signalization.