[Dottore]

I'm also not a huge fan of Frankfurt, but if you only have a couple of days there's certainly more than enough to do.

The old quarter is very charming. Great bars and restaurants and nightlife etc. Order some "handkaese mit musik" which is a local speciality. Some very nice old bars overlooking the river.

Then, on the northwest fringe of Frankfurt is Kronberg, which is one of the prettiest old towns in Germany. You can get there with public transport from the city center in only 30 minutes or so and its great place to spend a day walking around, enjoying the small bars and beer gardens etc etc. The "Schlosshotel Kronberg" is magnificent medieval castle that has been turned into a luxury hotel, and even if you don't stay there, you should have a drink or a meal there. Spectacular.

It depends how much time you have—but if you only have a short time I wouldn't spend this on trains to and from Munich. Unless of course you like trains.