I just wanted to find out how accurately I could recreate Doom OPL3 playback in SF2 format. The only thing I was not able to recreate is a different sounding due to the note length as it turns out for some instrument the shorter it is the longer it sounds. This is why this soundfont will not sound right with Doom2 titlepic music as "Synth Drum" preset was made out of long notes variant but it suits E1M8 perfectly because this song plays them longer. Doom Wiki says there is a minor difference between Doom and Doom 2 genmidi lumps while I noticed that there are a bit more of different instruments that the wiki points, these are presets # 29 (Overdriven Guitar), 32 (Acoustic Bass), 35 (Fretless Bass), 36 (Slap Bass1) and 58 (Tuba). Splash Cymbal is also different meaning that in Doom 2 if a note played was very short it will lead to more tonal sounding of such cymbal, this soundfont doesn't capture this effect unfortunately and it's best noticeable with D_AMPIE song (Map 23).
The downside of these are not just sound inaccuracies but also the file size, that's why there are also SFOGG (FalcoSoft MidiPlayer) and SF3 available that pack the soundfonts into a medium quality OGG:
Doom 1 (shareware, registered and ultimate doom):
Doom 2 v 1.9