A guitar player sent me two tracks. One is a nice chunky rhythm and the other is a lead played over top. They sound great alone but there’s very little room for the bass and drums inside the frequency spectrum. Any suggestions on how I can create the necessary room for bass and drums to come through without losing too much of the fullness and warmth of the guitar tracks? He recorded them direct in on a Stratocaster and I am using Cubase 8.5 Pro.
…EQ?
Without hearing, I’d be thinking the same as Larry. I think it’s common to use a low pass filter to cut the lowest part of guitars to make room for the bass and the kick drum. If you then listen to the guitars alone, you might think they sound thinner, but when the bass is there, the whole thing is much clearer, and the low part of the guitar is not missed.
Well stated!
{‘-’}
Plus, if you want to get really crazy…
If the guitars are mono, send them to a stereo group channel with the Cloner VST to thicken them up.
Then use an EQ with M/S processing to cut out the guitars in the mid channel but boost them a bit on the side channel. Since bass, kick and snare are generally panned dead center this will give those instruments room without sacrificing as much on the guitars. 
That’s what I do for solo voice/piano ballads: M/S the piano, boost the side/cut the mid by 2dBFS or so, leaving room for the voice while giving the piano a “free” boost it wouldn’t otherwise have.
Thank you all very much! I look forward to applying the guidance you provided.
And of course there are more modern approaches such as Wavefactory’s trackspacer - a VST which listens to one track and uses the sonic profile to subtract a chunk of EQ out the other in real time to allow the source track to cut through. It only EQs the affected track when the source sound is playing returning EQ to flat in-between. Lazy approach? Hell yeah! But it can save you a stack of time playing with EQ cuts.
Call Phil Spector? And get that perfect wall of sound 
HIs fees are murderous though 
I bet there are some wicked rooms where he’s currently residing that would make fantastic physical echo chambers that would be handy for the ‘Wall of sound’ errr… sound 
some kind of weird/poetic irony in there
Its a sad story all in all, but people change. 
That reminds of how much I liked playing my Les Paul un-amped in our fairly large bathroom, great sustaining reverb! And for the yanks, here in Oz we don’t doo and pee in the bathroom, we do that in the toilet !
If it added automation to the EQ bands instead of simply adjusting the EQ on the fly I wouldn’t be against this because you can always tweak things later to get the exact sound you want. But if you have no ability to adjust the EQ cuts being made then I am absolutely against this.
Update. When I cut the lows and mids it revealed the sound of his hand hitting the body of the guitar. Turns out because the recording was done direct in he actually had a clean track to send me so problem solved. I’m grateful you all put my focus on Eq and I had a great time learning what it can and cannot do.
I’m sure they will all sleep better tonight knowing this!