Oh wow... Playfirst closed their doors many years ago - they haven't made a game since 2005. It's the reason why their games never go on sale at Steam - because the company no longer exists. It's also why Big Fish does not sell their games anymore.
You should try the Delicious: Emily games by GameHouse. They're not as frenetic as the Diner Dash games (no chaining bonus for cleaning up, for instance), but once I got used to the style of the games, I was totally addicted. I have a whole section dedicated to the Delicious: Emily Games
, and have thoughts on the series posted here
Do you like TM's like the My Kingdom for the Princess and Roads of Rome games?