The last NEC-approved game was Dead Of The Brain 1-2, released around 1997. Nowadays, there are only two companies working on PC Engine games, and neither are approved by NEC, Hudson, or any of the other relevant companies of the day. Those two companies are:
MindRec
MindRec is the only post-NEC PC Engine development company to ever successfully release actual CDROM software for the machine. It's owned and run by Bt Garner, a scene veteran and a close friend of the people at
Turbo Zone Direct, the only remaining "official" marketer of new PCE/TG16 products. MindRec has been around for quite a number of years; their first (and so far only due to problems with pressing CDROMs in the required format) successful release was in 2002, which was a game called
Implode. They have several other games in the works, including a couple of shooters, an RPG, and a run-and-gunner in the vein of the original Contra games.
Frozen Utopia
This company was started by me and a guy named Richard Marks in 2005. The name was conceived by myself and our primary musician, Drake Woods. We have not had an official release yet, only the demo of Mysterious Song, but we have several other games in the works, including a couple of platformers, a top-down adventure RPG (Zeldaesque), a fighting game, and a side-scrolling beat-em-up in the vein of Final Fight.
That's it...there are no others out there, and believe me, I've looked. There are a few independent one-man-armies though; people like
Chris Covell develop games on their own, though generally without commercial aspirations.