Aside from the Roland Integra 7, I'm not aware of anything that has great electric guitar emulation.
 
I'd love to hear from you guys if you can provide some suggestions.
 
 

Air guitar is my favourite. No matter what musical style it always sounds spot on.

Of course this is very subjective....  you're going to get many different answers here..

Some of the Applied acoustic Systems VSTis (Strum-GS-2 and String-VS2) sound alright to me.  Though with these you do have to spend the time getting the parameters right.  They may not sound right out of the box.  You really have to tweak them the patches.  Also, it does depend of your keyboard skills and style to get them sounding right.

I've had some luck with ASS Strum after some trial and error and not using the built in Amp Modelling.  

Checkout Orange Tree Samples they have a large range of acoustic and electric guitar libraries for use in the free Kontakt player. 
 
I would say that for general use the Rock Standard or Stratosphere are probably the best (Les Paul, and Strat respectively) Strawberry is also a good all-rounder but they are all different and good. They all have a good range of articulations and setting up the velocity switching is easy.
 
Apart form the "lead" sounds The strum sequencer is intuitive and quite versatile.
 
They are sampled clean and use Kontakt's effect and amp sims for maximum versatility. You can also bypass the effects and use your favourite amp sim(s). Multi-track mode allows for up to 4 discrete outputs if you want to get adventurous.
 
 
 

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

Personally I find AAS Strum Session too fake sounding, unless it's very hidden in the mix.
 

Glyn Barnes
Checkout Orange Tree Samples they have a large range of acoustic and electric guitar libraries for use in the free Kontakt player. 
 
I would say that for general use the Rock Standard or Stratosphere are probably the best (Les Paul, and Strat respectively) Strawberry is also a good all-rounder but they are all different and good. They all have a good range of articulations and setting up the velocity switching is easy.
 
Apart form the "lead" sounds The strum sequencer is intuitive and quite versatile.
 
They are sampled clean and use Kontakt's effect and amp sims for maximum versatility. You can also bypass the effects and use your favourite amp sim(s). Multi-track mode allows for up to 4 discrete outputs if you want to get adventurous.

A good choice - for Electric guitars also check out:
 
Shreddage 2 by Impact Soundworks
Electri6ity by Vir2
RealStrat / RealLP by MusicLab
Amplesound guitar series
Native Instruments Session Guitarist Electric Sunburst
 
Orange Tree as mentioned by Glyn are probably the best, but also very pricy. Personally I went for Shreddage 2 as it was the best bang for buck at the time (I got all 3 models in a bundle for $99).
 
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.
 
For more immediate results (if somewhat more limiting) also look at the VirtualGuitarist series by uJAM. This I do use regularly as it's so easy to get a great sound right away if I just want strumming or basic power-chord riffs.
 
Like I said, the learning curve for most is huge - not that they're hard to use, just hard to get good results without lots of editing and tweaking. I guess this gets quicker with practice.
 
What I personally do for stuff I can't play (like crazy fast sweep picked scales), is use a combination of Revalver's pickup modeller and Overloud and:

• Model my own guitar with Revalver
• Model Shreddage 2 with Revalver
• Play most of my parts using a real guitar
• The bits I find impossible to play, do with Shreddage
• Run both the modelled guitars into a bus, with Overloud on the bus... they sound like the same guitar

M.
 

I am a huge fan of Shreddage.  I have both 1 and 2.  I use 1 for the crunchy rhythms (1 isn't made for leads) and I use 2 for leads.  I'm not a fan of 2 for the rhythm, though it does work for that...I find 1 easier to use for it.   

I use Vir2 Electri6ty but the trick to making it sound more guitar like for leads is putting it through a good guitar amp/cab sim plugin instead of its built in guitar amp fx which I personally think makes Electri6ity sound weak.
I use Kazrog thermionik amp sims, there are round 30 odd amp sims of different tube amps and I use two note wall of sound for the amp cabinet sims. I should add I'm also a guitar player as well as keyboardist but for the nice guitar like keyboard soloing I use Electri6ity although I also think Orange Tree Evolution Infinity is probably better has you can trigger harmonics and feedback which will add a bit more expressive realism to a keyboard solo. If I could have gotten those tones back in the day, I probably wouldn't have taken up guitar.
 
I've done a little demo of Vir2 Electri6ity lead playing here:
 

 
 

For acoustic guitar, I believe AmpleSound is better for their strumming and chord technology.  I have their Martin and Taylor models as well as their Taylor 12 string.
 
For electric, I have AmpleSound's Les Paul, Stratocaster and Telecaster.  I also have Music Lab's Les Paul and Rickenbacker 6&12 string models and also their 8 string model.  MusicLab's guitars have a great set of articulations, such as unison bend, feedback, etc.  The feedback is amazing and sounds very realistic.
 
For bass, I used to use Trilian, but now I use IK Multimedia's MODO Bass.  It uses no samples and is physically modeled.
 
I use Amplitube 4 for amplification for the electric guitar plugins and for my real electric guitars as well when I'm not mic'ing my Orange Crush RT-30.