I don't know whether the PS3 will end up selling better than the Gamecube but the logic behind the arguments "The PS3 started out at a higher price" and "The PS3 will have a longer life" which lead to it (some how) having higher sales is flawed.
The first 18 months of a console's life are critical because it establishes a sales pace which determines the level of third party support. While it is true that the PS3 is more expensive this also has the effect of keeping it out of the price range of the average consumer, and thus causing slow sales, for 36 or 48 months; if in most generations 18 months was too long to wait for a recovery I'm positive that the PS3 will be seeing a really bad software drought by its 36th month. How many people rush out to buy a $300 console with no games?
Back in the day Nintendo claimed that they thought the Gamecube would last 8 years, after 4 years the system was coasting on fumes; the Wii is similar to the Gamecube in terms of processing power so we can assume that (since the Wii is selling well) the Gamecube's shorter than expected life had little to do with how powerful it was. Because of lower than acceptable initial sales third party developers found any excuse they could to not develop for the Gamecube and thus consumers were unwilling to spend the $100 to $150 to buy the system (even though many amazing games were released for it).
Basically, if third party support tanks due to low sales the PS3 is in a tough position because it is so expensive that few people will even consider buying the system for a handful of games ...
