The Bonnevile Shoreline Trails (BST) are the best IMO because they aren't too steep. Many other trails in the WF go up/down canyons, and there is limited "running" you can actually do on them. The Little Cottonwood creek trail is also very good. There are some cool trails out on Antelope Island as well, which seem to hold less snow in the winter.
+1 for the Little Cottonwood creek trail. In the heart of winter it is a nice lazy snowshoe spot, great for families. In the fall, spring, and summer it is a great trail running spot.