Here's my take:
EQ is the single most important factor in a good mix. A close second is compression.
Everything you record gets EQ'd in some way or another. Those with the resources and knowledge make EQ choices when they choose a particular mic or pre to record a given instrument with. You can also make EQ choices when you choose a room to record in. You make EQ choices when you pick which guitar sounds best on a particular song. Hopefully, if you have enough resources and wisdom to make all those EQ choices correctly at tracking time, mixing will be much simpler. It's always better to get a good sound up front.
In the real world we all face limitations. Let's face it: most homereccer's don't have the the means to get the exact sound needed in tracking. Mixing EQ is an absolute necessity to make tracks work together. That said, it should always be approached conservatively.
Furthermore, as TexRoadkill said, getting a realistic sound is not always what you need. In the pop music world, a good
acoustic guitar sound is almost never and accurate reproduction of what an
acoustic guitar sounds like. (or electric for that matter). There is almost always some low end gone to make room for snare and bass, among other things, and somewhere along the line an engineer made that EQ choice, either with mic, pre, room, EQ device, or some combination of those.
got mojo?
www.voodoovibe.com