I did a game called minefield that was a rubbish minesweeper + knobs on game. It sold maybe a dozen copies.
I did a top down car racing game called Kombat Kars, and one called Rocky Racers. They were good games, very popular with downloaders, but I think people didnt see there to be enough *game* to be worth actually paying for.
I thought Planetary Defence was a good game, one of my better games, but it doesn't sell anything like as many as it could. I'm not entirely sure why.
But I'm past worrying about any of these, concentrating entirely on my more successful and fiture games.