That is akin to asking "Are there an great guitar amps out there?".
 
My answer for both questions? "Only about 3 or 4 dozen to choose from.".
 
Anyway, look above this post for all that I would have mentioned.

Indiginus

MusicLab

msmcleod
 
Amplesound's range is great for acoustics, and also IMO the easiest to play.
 
A word of caution though:
1. Most of these require the full version of Kontakt
2. Although these emulations sound fantastic, covering every technique you could imagine, the learning curve is huge. Unless you're a wiz in the piano roll editor, it'll take you ages to get the results in their demos. In most cases I've resorted to practicing on an actual guitar and playing it myself... cos it's quicker!
3. The in-built effects while adequate aren't that great. You'll probably want some other guitar rack suck as GuitarRig5/Amplitube/Revalver/Overloud. This is down to taste - I tried them all and I tend to go for Overloud, which I upgraded from the CW verson to the full version.

The cautions in this posts are worth repeating. The only VSTi I have purchased is Heavier7Strings which was more to get the 7th string without another guitar. That has a standalone version that plays nicely through WindowsAudio without issues (no Kontakt needed, or ASIO). Downside is #2 above, since their demos are done with Cubase, which has slicker access into the keyswitches required to play it realistically; but again, you will need some savvy in the PRV to access the full capabilities.
 
Recently I have also been trying AmpleSound's free acoustic (AGML2), and that also falls into the same bucket functionally.
 
I am not a Kontakt fan, so cannot speak to those requiring the "full version of Kontakt," but that is something to take into consideration with your choices. As I have been doing scoring more lately with Notion 6, I have taken to both H7S and AGML2 since they are fairly lightweight as VSTi inserts, but Notion does not have good access into the keyswitching required to play them realistically.

I really appreciate all these answers, people.  I had no idea there were so many to choose from!  
 
I'm not intending to buy NI, so I'll consider the other options.  

If you're not needing any special articulations (e.g. pick squeals, false harmonics, slides, hammer-ons/pull-offs etc), the Rapture guitar samples that came with the Cakewalk 30th anniversary are very usable when put through Overloud.
 
Also look at adding the "Bridge Hum to SC" FX chain from the "30th Anniversary Anderton Collection" (put before Overloud) to get a more strat-type sound.
 
Worth taking a look, as it'll not cost you anything.
 
M.

Songroom
NI Session Guitarist Electric Sunburst is worth a look...
 
Audio demos

I have just bought this - tell you what, it's extremely flexible and is awesome with its own fx and amp sim OFF, and played through S-Gear.

I have more than a dozen electric guitar libraries. Why so many? Because the guitar is a versatile and expressive instrument, and sampling one only provides a snapshot of what any particular instrument is capable of. So you end up with a bunch of them, each one specializing in a subset of the guitar universe.
 
These are the ones I use most...
 
#1 on my list is Orange Tree Samples' Strawberry. Not because it's necessarily the best, but rather because it happens to suit what I do the best. If you're into chugging metal rhythm guitar, Electri6ity might be a better choice. The OTS Strat is also very good for expressive leads, but I keep coming back to the Strawberry.
 
#2 in my toolkit would be Indiginus' Renegade. Not as versatile as the OTS libraries, but much less expensive and simple to use because it has a great sound right out of the box. Also look at Indiginus' Torch, a similar-sounding instrument.
 
#3 isn't even an electric guitar, but rather an acoustic. However, I normally run it through an amp sim and use it as if it was an electric guitar. That's Indiginus' Delta Blues Slide Guitar. Very expressive for leads.
 
#4 is the OTS Rickenbacker 12-string. Sounds like the real deal. Great for classic rock, which is my preferred genre, so this one gets used a lot for both rhythm and leads.
 
Honorable mention: SampleLogic's Cinematic Guitars series. These are more for texture and underscores, but they create sounds I can't easily get with any other guitar library or synthesizer.

I consider MIDI triggered sound libraries as temporary stand-ins for real performers. It's always a good idea to have seasoned professionals to play on your tracks, whenever it is possible. For that matter any decent virtual instrument is good enough for demos or even commercial but not top of the line records.