For the sake of discussion, let's stipulate that all of the objective factors are good or great. That would be fretwork/crowing. It's set-up well with great action, intonation, and everything functions as it should.
I'll also, for the sake of discussion, dismiss the subjective points which are different for everyone.
So with that in mind, IMO, a great (electric solid body) guitar starts with a great piece of body wood that is light and not too dense.
For what I value, great guitars are light. And that's not just my ergonomic personal preference. Lighter guitars with less dense wood tend to be more resonant. In my experience, it's very hard to get resonance out of a guitar that weighs 9lbs or more. You'll get sustain from dense wood (and other factors), but not resonance.
There are some genres -- particularly in more extreme Metal, where resonance isn't a tonal requirement (if you're all gained out and scooping your mids, etc). You don't need a particularly resonant, or great sounding guitar for that stuff.
But by "great guitar," I mean a guitar that will sound great in ANY musical genre. And IMO, resonance is important, and a key component to a great guitar. A resonant guitar rings out loudly, and pleasingly when played acoustically. You can usually feel the string vibrations going through the guitar body. And this quote from the old Mr. X interview still applies:
(You're looking for) fullness of tone in the three ranges — high, medium, and low. And overall smoothness, rather than one frequency that sticks out in a pronounced or unpleasant way. You're listening for roundness of tone. You don't want (the tone) to disappear into bass frequencies, or go into that ratty high-end scritch tone.
And FWIW, guitars that produce this fullness of tone across frequencies will support lighter string gages (8s or 9s) and still sound great. They won't need heavier strings to produce great tone. They'll also usually respond well with any pickup you choose because you're just enhancing what the guitar is already producing acoustically.
So how does this play out in the real world? There are always exceptions, but on average, great sounding:
- Strat style guitars tend to be in the 7 to 8 lb range.
- Teles, SGs, and Vs tend to be even lighter -- often less than 7lbs, rarely approaching 8.
- Non-chambered Les Paul's, on average, tend to be in the 8.5 lb range.
Again, from the Mr. X interview:
(Heavy Les Pauls usually have): a lot of bright top end — generally — there are always exceptions but I'd say in most cases. And a booming low end. With no warm midrange in between.
So a great guitar is light, resonant, and produces fullness of tone across high, medium, and low frequencies. And FWIW, that's true of acoustics as well.
Once you have that, you're also looking for good sustain. But whether you're getting it from a Tele's bridge pan, a Strat's trem block, a LP's maple cap, or a super strat's Floyd, sustain is comparatively easy to come by.
The trick is to get your sustain without upsetting the tonal balance we've already discussed. Sometimes there's a trade off. Like the way a Floyd Rose always audibly changes the tonal characteristics of a guitar. But if you need a Floyd, you need a Floyd. And there are plenty of great sounding, Floyd equipped guitars. But FR guitars tend to be unitaskers, and you don't see a lot of FR guitars outside of the Dino genre.
A great guitar also FEELS great.
Again, if you throw out the subjective, personal preference aspects and generalize, a great guitar just feels right in your hands. Playing a great guitar feels effortless to compared to lesser guitars. Things you normally find hard to play, are easier to play on a great guitar. When you demand something of the guitar, it gives it back to you with ease. You never have to fight for it. Once you start playing it, you don't want to stop. It's hard to put it down. And when you're not playing it, it beckons you to pick it up again and play some more.