Up thru #21, I've played a wopping 13 titles. I realize it's going to be hard to compare the relative merits across platforms and decades, but there's clearly some problems with the list.
A legit top 6, in no particular order:
Tetris (how many ripoffs have followed?)
PacMan (had its own tribute song in the top 40!!!)
Doom (introducing the FPS)
Myst (sold how many bazillion copies to non-gamers?)
Pong (started it all)
Starcraft (Koreans are dying from playing 72+ straight hours)
More Likely top titles on this list:
MW
One of the Final Fantasy titles
The first major Mario title
Diablo