We have 5+ days to travel from Paris to Basel, Switzerland where we will board a river cruise in August 2014. We are open to driving (renting a car) or taking a train but want to see as much as possible. This is a new area for us but we are adventurous and open to suggestions.
One suggestion would be to spend a few days in Colmar, as it's a beautiful city and makes a great home base for exploring the eastern wine region. Strasbourg is also worth a day trip, especially to see the incredible Cathedral.
Ditto Ken. Colmar is very scenic. It's also reasonably close to Basel.
These are great ideas. A car would be useful while you're in Colmar to tour the surrounding villages, but when you get ready to head to Paris, please take the TGV (fast train) from Strasbourg. It takes only 2 hours and about 20 minutes, which is MUCH faster than the time it would take you to drive it. Plus you arrive in the city center instead of having to face the dreaded Paris ring road. Buy your tickets in advance for substantial savings on price.