It's still too early to talk about which couples will be the most interesting, although if you look only at the names Borussia - Leverkusen, it will probably be out of competition. In the pair Frankfurt - Bavaria, in my opinion, Frankfurt is in great danger 
as Bayern will try to prove that this pair does not play the winner of the Euro Cup with the loser of the Euro Cup, but the current champion with an ordinary club.
I expect already a clear statement from Bayern in their first game in Frankfurt. This won't be the easiest pairing for Bayern, but they'll probably get a 3-0 win already which will devastate the competition from early on. Borussia vs Leverkusen is a top game if you look at the ranking last year. Somehow I expect one of these two teams to perform poorly next season. Cologne vs Schalke and the Berlin Derby look more interesting to me overall. as Bayern will try to prove that this pair does not play the winner of the Euro Cup with the loser of the Euro Cup, but the current champion with an ordinary club.