To me, a good track is one you're happy with that works in a mix of other instruments. Not to go against the grain of what everyone else has mentioned, but I've heard some terrible performances actually turn out to be acceptable once the sounds were tweaked.
I don't think Neil Young or Kurt Cobain are/were good guitar players from a performance or technical aspect. However, both have achieved some pretty good tones that exceeded their actual performance.
Though I'm in the camp of the best performance you can get, there definitely are instances where someone that may not have played very good got away with it due to a solid tone being created.
Good gear vs bad gear? All in the ears of the person creating the sound. I've seen some really bad stuff come through that surprised me once we printed it.
Knowing what a good sound and what isn't is just something that takes time. The more you do this stuff the more you know what will work and what won't the instant you hear it. Until a person gets to that point...my rule of thumb is, if you spend an hour tweaking something, chances are it's not a good sound. That said, it may take you 2 hours to mic something the right way while experimenting. That's a different animal than tweaking tones that were already recorded.
The reason for a good tone is so you don't spend loads of time making it work within a mix. You'll just about always have to make little tweaks here and there, but with good tones they should always be minimal. :)
-Danny