Instead of the M Steakhouse, you could also try the Surf & Turf (same internet address).
Not quite so exclusive is the Sky Lounge (www.skylounge.info).

The Japanese restaurant at the Frankfurter Hof, Ihora, is supposedly very good but also very expensive. www.iroha-frankfurt.de

Try the Mayflower (www.mayflower-chinarestaurant.de) for Chinese.