The obsession with 'stereo' always surprises me - with the guitar, as said by garb, guitars aren't much more than a point source, but worst is when people take something like a piano or vibraphone and mic it wide, with a kind of hole in the middle, and then as the player bashes away, the image seems to make the instrument as wide as your entire listening room - and when they go up or down the instrument fast, the notes gradually shift from left to right - sounds majorly strange to my ears.
I solved that problem by using a 3rd, center mic when recording my upright in stereo.
I do a spaced stereo pair with the bottom, front panel open on the upright...and then I add a center mono mic up top, with the hammers/strings exposed. Basically...I usually remove all that cover wood top and bottom.
So I get the wide L/R spread...but there is also a solid center, and you don't have that hole.
Of course...that works best for songs/mixes that are more sparse and allow a wide stereo instrument to exist in all that space without causing clutter.
For guitars (and I guess you guys are talking acoustic guitar, but I mean for electric)...I've done stereo recording using a few different stereo miking methods...but the one that worked out really well, on a 212 cab with the mics dead center between the speakers and about 2' back...was a Blumlein mic set, using my two Cascade Fat Head mics.
You don't get any hard L/R thing...it's still all centered and sounds mostly like a mono/single point-source...but it adds a 3D fell to the sound of the guitar. This was/is mostly for lead guitar tracks...not rhythm.
Again, it was for a song with a sparse mix, where that 3D quality could be felt. In a very full mix it wouldn't be noticed, and for those, I just record guitar leads in mono....or if I use two mics, I end up piking one or blending them to one track.