I think there is like 20 or so games.. BUT the EXCLUSIVES that never had a retail release are very few. I think there is like 3 or 4.
Super Famicom Wars
The Japanese version of Super Punch-Out!! (I wonder if it was meant to be released at the same time as the western versions, as the western version has a Japanese naming screen, accessible with a code. Which would be a strange thing to put in otherwise.)
Dokyusei(?) 2 (is that a hentai dating game? Or was it, as I would imagine, censored?)
The NP Picross series
Not sure if Metal Slader Glory was NP-only. I know there was a retail release, but was that a MaskROM cart or a pre-loaded NP cart with a special label?
Ogre Battle seems to have gotten an NP-only update. I don't know what the difference is but the NP ROM is 512KB (one NP "block") larger.