Living most of my life in the Portland area, I have been to Multnomah Falls many time. I am still amazed as the massive water. But there's a lot of exploring to do behind the falls. After you've hiked to the bridge, keep going. There are miles of hiking trails, all beautiful and away from the crowds. The views from the trail are fabulous, looking out on the Columbia River Gorge. Also don't miss the falls in the winter. The spray forms ice all around the falls making it a true winter wonderland. You can pick up a map at the gift shop.
Pros: beautiful natural setting, parking, hiking
Cons: weekends are busy