The very sad thing about some video games is that they're not very good, but the idea behind them was so good that in the right hands they could've been groundbreaking. That's the really depressing part, a bad game that was always going to be bad is one thing, but bad games that could've been good hurt even more.
I personally can't help but feel that Brink could've been an amazing game, and while Lost Planet 2 wasn't a bad game and IMHO was more of an ok game, I feel like in the hands of better writers, the countless factions on EDN III could've been more developed and we could've been given a deep rich world. Sadly though, the only thing that's really different about the various factions are their uniforms (which are admittedly nicely designed) and the toys that they have.
What about you? Which bad or mediocre games have you played do you wish had been more well developed or better programed.