Bayern-Arsenal should be interesting even if it is as one-sided as everyone predicts. I expect Lahm to suffocate Ozil as much as possible and Pep to have Bayern dominate the midfield entirely. I can't pretend to know what to expect in Pep's lineup as they have a lot of depth but he has so many options he can use that Arsenal will not know what to prepare for and which asset of Bayern's game will deliver the dagger blow.
As for Atletico-Milan, it's not difficult to see what will happen unless Atleti go down like they did against Real in the CDR. Simeone should take that as a wakeup call and be certain that he can't let that happen to his team in a competition like the CL.