Agreed with Wyndham: If you can afford Real Guitar, it truly is great. But there are a few really nice freebies out there, like Spicy Guitar and Flamingo. And, like PGF and rHarv said, processing the raw guitar sound and playing with the MIDI file itself can help a lot. I have also found a few really good soundfonts, but bluntly the best of those are commercial, from Sonivox, and they've put most of them into much-easier-to-use plugin instruments nowadays.

Best,
Tom Smith
Win10/64 • i7-8700K • 24 GB RAM
BIAB 2025 • Reaper 7 • Izotope MPS
AKG C1000S • IK iRig I/O Pro