Disagree. Because I own both Flight1 ATR 72 and Captain Sim C-130, and I find avionics more realistic in X-plane then in FS2004/FSX. Yep, I did fly in RL alone. Yep, I did fly on instructor seat plenty times in ATR72 and 42 and observed how it compares to FS2004/FSX "high fidelity added avionics" (X-plane wins already with stock avionics).
In this case, because you are looking for heavy airliner try researching project x737 and all the additional payable software for it.