depends on the models honestly...
audiotechnica ad500/700/900x series... bass light, huge soundstage, great positional audio. more treble and mids based profile.
audiotechnica athm50 and similar... fairly bassy, small soundstage even for closed headphones, warm sound signature, v-shaped sound profile.
beyerdynamic dt770. like m50 but with bigger soundstage and a bit more bass with slightly sharper treble.
beyerdynamic dt880 neutral profile otherwise similar to dt990.
beyerdynamic dt990 nice wide soundstage, clear crisp detailed treble (though some find it bright) and good bass for open cans. v-shaped sound profile.
sennheiser hd518/558/598 okay to good soundstage with neutral sound (ranging from more bassy to completely neutral 518->598). smooth/easy listening.
most akg cans.... not much bass and sharp piercing treble but large soundstage. comparable to ad-series from AT but with more treble.
..dont really know much about the grados..
v-moda various models tend to be a little on the bassier side like m50s
not mentioned are the budget choice CAL!, some basscannon class headphones and some of the closed headphones from AT/Sennheiser.
and unlike what i7b stated you CAN often find frequency response charts (despite not always being provided by the manufacturer) as many headphones get tested by 3rd party websites which specialize in that sort of thing. some of them are extremely well done and in depth. while interesting, the more practical side of "yeah, but how do they sound?" is generally going to be more important which is why i listed a few characteristics above.