Imo, actually Medieval 2 was the best; to get the most out of that game though you want mods (aka modified files by players that have created campaigns).
The best mod, imo, is Stainless Steel, incorporate it into your campaigns...SS has only a few bugs too. However the graphics are old, but there are programs (I don't recall atm names) that can enhance the graphics to more 'of the day looking games.