RKB
For many years I tried various samplers, synths, software, etc. trying to get guitar chops out of a keyboard. Even though I had some basic guitar chops, I wanted to stay in the MIDI environment and I wanted to avoid buying guitars, amps, mic'ing amps, etc. etc. etc.
I came to the conclusion - it simply can't be done well! While you can get realistic solos, and even single pickin' (even power chords - to a limited degree) but trying to get realistic rhythem guitar riffs on keys is not a realistic goal.
A simple open E chord on a guitar covers over 2 octaves (very wide voiceing on a keyboard) and trying to get "strums" or "muted strums" is a trick not designed for keys. (The site minofifa suggests looks like it could be of help to you).
After much effort and expense (on sample libraries, etc) I finally started to spend an hour or two a day to get my guitar chops to a point that I could play the parts. It was much work, but satisfying (more satisfaction than loops and samples that never sounded quite right).
Naturally, I now spend money on guitars and amps instead of sample libraries, and I have yet another instrument to continuously learn - but I never claimed this was a good plan
