The best meal I had in Berlin was at Ganymed brasserie on the Spree, within in stone's throw of the Berliner Ensemble theater.
http://www.ganymed-brasserie.de/I also enjoyed eating lunch in the garden of Cafe Einstein, but more for the ambience than the food. (The food is fine, but it is classic German cuisine, which is not my favorite).
Although it is surely in every tourist guide, I believe the Reichstag is one of the most extraordinary sights in Europe and deserves a lingering, detailed tour. I also think that going to the section of the Berlin Wall that remains, and the small museum across the street, is quite worthwhile.
I also went to the Bauhaus museum, but I am a Bauhaus nut. And I wished I had spent more time in the "West," which is stuck in a 70s time warp.
But almost every step you take in Berlin in fascinating, and the standard tourist attractions don't disappoint.