It depends on your definition of "complete".
Half Life still needed a lot of optimization and suffers from slowdown in places, long load times, and a glitch that causes save files to increase in size every time you save.
ToeJam and Earl was maybe about 75% complete. The game is playable for the first nine levels or so with some slowdown in places but will eventually crash.
Geist Force wasn't even close to completion; the levels are all there but it suffers from a lot of slowdown, it crashes very frequently, and a lot of things are missing (enemies, textures, a menu, etc.).
PBA Bowling actually might be complete but I'm not sure; I haven't playing much of it.
Hellgate made it to a beta stage and while most of the game is there, it lacks polish and is quite buggy (I haven't actually played this one).
The Flintstones is hard to tell because it's really just a horrible game. My guess is that it's not quite complete though as it has slowdown in quite a few places, especially when shooting enemies. It could also use a lot more polish.
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The Games That Never Were is the series about cancelled Dreamcast games.