Naah, not O'Reilley's, try McGowan's in Bornheim, or An Sibin in Wallstrasse (often has live music), for better craic.
OK, so it's pubs then. 'ere we go: Apart from
- the "Fox" Pubs
- the Irish ones (see above - there's another McGowan's at the far end of Zeil)
- the Apple Wine places, very traditional German and often with very nice outdoor seating, namely: Gemaltes Haus, Wagner, Germania, Fichte Kranzi in Sachsenhausen, Stahlburg in the Nord End, Sonne and Solzer in Bornheim
- the Cocktail bars: 21st Jahrhundert, Oder Weg (near the Multiplex cinema), Rote Bar on Mainkai, Minibar on Berger Strasse, Vth
Element near Eschersheimer Turm.
- for breakfast, try Café Karin (near Goethe Haus), Metropol (behind the Cathedral), or Ypsilon on Berger Strasse (esp. good for Sunday brunch).
- in other news, Turmpalast Cinema near Eschersheimer Tor has US and UK movies in English (i.e. not dubbed in German) on 7 screens, but the qualilty of both sound and image in Turm 3, 4, 5 and 6 screens is outright horrible, while 1, 2 and 7 are only just acceptable. Berger Kino on Berger Strasse has some movies "im Originalton" (not dubbed) and generally is much better kept, so check listings.
As a rule, AVOID the "Bahnhofsviertel" red light district (that's easier said than done, as it's located right across the street from the central train station).