Call me crazy, but...
Frankly, I didn't enjoy Doom II's music as much as I did its' prequel. Bobby Prince's strange yet palpable music for Doom was worth listening to outside of the game, but Doom II?
In most of the midis, you get about ten bars or so that get repeated endlessly throughout the track, with a few variations in pitch/sound in an attempt to add variety. Some of the tunes are catchy, but there's so little repetition it quickly becomes irritating listening to the same stuff over and over again. It's like "The Song that Never Ends" that kids used to sing at my primary school.
Another problem is that most of the midis are quiet and underspoken, which might be appropriate in a horror-based survival game just doesn't cut it with Doom II's demon-blasting gut-wrenching non-stop action. There are some decent midis in the game, but this definitely isn't music that belongs in a game like Doom II.