The Roland SRX 02 expansion has been the closest experience to a real grand piano for me. It really conveys the warm, wooden sound of a mellow European grand piano, possibly sampled from a Bechstein. It‘s about the only one that has made me feel sitting in front of a real grand piano.
But it wasn‘t very popular as it only sounded good through headphones, otherwise too mellow, and it had too sudden „jumps“ in timbre between the four velocity layers.