Indeed, the PS2 numbers will be impressive until something gives a match-up worth noting.
Take a look at this chart. Note the DS line, which seems to be having a better lifespan so far than the PS2. The DS, entering its 3rd 'real holiday' (first ones are usually short for demand so don't get an accurate sales reading) is still rising in average weekly sales. This same point in the PS2's life span, it has peaked, and the overall longhaul for the PS2 after this compared point in time is a steady downfall, slow but surely.
The DS is more fact now, due to its increasing popularity and still decent demand. The challenge for a video game platform to surpass the PS2 would likely by the DS at some point.
The Wii, however, take a look at the outstanding weekly sales compared to the PS2. The Wii is roughly selling 5-6 times as fast as the PS2 did during the period before the first major holiday season.
While the Wii has been out for not even a year, its sales blow away the DS so far, the only real competitor by proven timespan to make a dent in PS2's title.
The real question will amount to whether or not a Wii revision occurs. I have always stood firmly on the idea that PS2 revisions and reading errors (replacements) really fluff up this near 120 million sales record.
Back to the real question, will Wii hardware fail and force consumers to buy new consoles and improve 'sales figures'? Will Wii2.0 be released as a smaller version with native 720p and DVD support, as well as larger flash space? This can also fluff numbers equally as well.
Numbers: Checker Players > Halo Players
Checkers Age and replayability > Halo Age and replayability
Therefore, Checkers > Halo
So, Checkers is a better game than Halo.