The first? <img src="/ubbthreads/images/graemlins/think.gif" alt="" />
Long time hence...
The first one with RP elements was 'Larn' - originally Unix-based, monochrome, "graphics" all dots and letters, played on an XT under DOS 5.0 (or was it still 3.3? My memory fails me...)
Whether that counts? I don't know - it lies in the 'eyes of the beholder' <- which would probably qualify <img src="/ubbthreads/images/graemlins/winkwink.gif" alt="" />