not necessarily, the ultimate megadrive soundfont is a good one.

The thing about sountfonts is that they are made to be used for GM/GS MIDI files, so you don't have to account for all variations that are possible with FM synthesis. Its like using OPL3 as the default MIDI driver in Windows 3.11/9x - it will map the GM instruments so a set of predefined parameters so you only really have 128 different variations.

that's about all I'd need, I use soundfonts with foobar 2000.