My Top Dog 4's would be:
Hale. Easy trail with good water stops. There's just no good view!
Osceola: Decent trail with water (unreliable) near summit.
Pierce: Good footing, just not a lot of water.
Eisenhower: Good footing until the dome. Unreliable water at one tricky section near treeline.
Carter Dome/Hight Loop: Water almost all along 19 Mi. Brook and near summit of Carter Dome. Footing okay most of the way, but lots of steps up to Carter Dome, then one short step section off Hight. Water along Cater Dome trail.
Garfield: Good water stops. Only a few steep steps on ridge trail.
Wildcat D via ski slopes: Very dog friendly, but almost no water.
Liberty via Liberty Springs: Lots of rock steps. Water at campsite. A few short steep steps near summit.
For non-4's, my dogs enjoyed the hike to Flat Mtn. Pond, Greeley Ponds, anything along Livermore Road, and the Smarts Brook loop. Basically, anything involving water!