Wow, looking at those numbers, no wonder why >U/Riley is always so pissed at Valve. They have over 240x the number of players as his game (FEAR) does. 240 times!! I'd add the NOLF series, but it looks like FlatOut2 and Flight Simulator 2006 beat it out for the top 40 spots.
He's too busy writing screeds about Valve's evilness to make compelling games that stand the test of time.