To my knowledge, Spectaculum closed shop a couple of years ago (mind you, I last went there when Katrina struck New Orleans, so it may actually have been quite some time!). It was all gone in 2012.
There still is (or was in late 2012) T3 - Terminal Entertainment near Hauptwache station (exact address: Grosse Eschenheimer Strasse 41a), which is a very nice combined comic books/gaming store - European, UK and US comics, and a good selection of various small figure ranges usually not found in game stores.
Furthermore, there seems to still be a comic book store (mainly European stuff in German language, though) on Berliner Strasse 20, close to the Römer, Cathedral and Museum of Modern Art.
Apart from that, Frankfurt has slim pickings when it comes to gaming. A very active and high-quality community, but little in the way of shops. Of course, there's a Games Workshop just north of Konstablerwache station, but that one's got nothing that you haven't seen before (although the staff were nice enough).