i agree that you should cut muddy or offending frequencies but to liven it up, i always refer to this.
"EQ ON RHYTHM GUITARS IN MIXDOWN
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I usually find when mixing that i nearly always put a stereo Massenberg GML 8200 EQ across the rhythm guitars, if the sound has been recorded cleanly ie no strange fizz or bottom end boom, then the same type of frequencies tend to be boosted on most of my mixes. Frequency wise it's usually around
8-10 khz for the air 4-6 khz for the bite area, usually 1.5 khz for the in your face effect, 400hz for the note of the guitar, and around 70-100 hz to pick out the weight of the cab.The boost amount just depends on what has been recorded, just turn it till it sounds good. This method has worked on many albums i have worked on including Heartwork Carcass, Burn my eyes Machine Head, Chimaira self titled, Bullet for my valentine, The Poison."