I'll pick one song from each game to avoid clutter
Really unique song for a shooter, never heard anything like it. Best soundtrack this gen.
The Black Label arrange improves Galuda 2's OST tenfold. This is probably my favorite track.
Death Smiles 2's OST is
extremely underrated, much like the game itself. This was the hardest game to pick just one favorite from, since nearly every track is fantastic.
Best stage 1 song from any game, period. Never gets old.
Namiki peaked in 2002/2003, when he composed back to back masterpieces with DOJ and Ketsui. Almost chose the stage 1 theme over this though, the vocals set the mood for the game perfectly.
The boss theme to end all boss themes. Shit just got real.
No surprise that the best songs in DFKBL were composed by Namiki (stage 1, stage 5, character select, and stage clear IIRC -
though stage 4B's song is awesome because of how insane it is)
So good.
I haven't put a lot of time into Garegga, but this song stuck with me since it's so awesome.
To summarize this post, Manabu Namiki is a VGM god. (And Ryu Umemoto could've surpassed him if he didn't die in his prime.)