The fact that you like the other 4 makes me wonder if you've ever seen True Romance. It's not what the title would lead you to think. At all.
At this point it's just repeating what others have said, but the most obvious ones are:
While I like many of the other ideas mentioned, these 4 really stand out as games that it's almost shocking were never made. I know the HP license was pursued, but denied. I have no idea if any of the others were gone after, but if not, it boggles the mind. At least it's easy to pretend that Johhny Mnemonic is actually The Matrix!
Also, not up there with the others, but I'm kind of surprised Stern hasn't gone for the Fast and the Furious franchise yet. There are plenty of movies now, and they don't seem to be slowing down. This would seem to be right up Steve Ritchie's alley...could be an awesome "continuation" to the High Speed series and has major appeal to the demographic they should be aiming for.