With two weeks I think heading to the San Juans would be worth the drive. Good areas would be
1. Wimenuche Wildernes – Very big and wild area for CO. There are a number of loops you can put together.
2. South San Juan Wilderness – I've not done this but its another big wilderness area and the drive in might be a bit shorter. Not as many loops as I recall.
3. Colorado trail from Spring Creek Pass to Durango – Most of the CT from the Pass to Durango is very nice. You could hike the CT north from Durango to Molas Pass then go down and catch a train. Another idea would be to hike up from Durango then loop through part of the Wimenuche wilderness. You can go up the CT on through Elk Park cross a pass and come out through Chicago Basin to catch the train.
You could also consider the Sangri de Cristo Range, and the Maroon Bells (scenic but a bit more crowded).
With two weeks would you consider heading north to the Wind River Range? Its a bit farther then the San Juans but you'll lose a day or most of a day driving no matter what.