Everyone has played that one game that was a complete mess but had one single spark of creativity that you wish was incorporated into a better game, maybe a series you like.

Example: I wish Driver San Francisco, or whatever next one they make, would take level design cues from Wheelman. For those who don't remember (i.e. everyone) Wheelman was that driving game starring Vin Diesel from a few years back that nobody played.

They both had an "arcadey" feel and a car hopping mechanic, but the thing that set Wheelman apart was being able to take shortcuts through buildings and to use ramps to jump from one road to another often at different heights. In Driver SF I lost count the amount of times I hit an invisible wall in midair, if they'd add this verticality to future maps the game would be just about perfect to me.

So what bad game have you played that had a great idea and what game do you wish would learn from it?

Jurassic Park: Trespasser had tons of them and actually influenced the gaming industry in it's own right (the Source engine).

There are many more, but I can't recall them at the moment.