Sony currently holds the console record, having already sold over 100 million units of the PS2. At the end of their fiscal year, in March '07, Sony expects to have sold 11 million PS2s as compared to a very rosy prediction of 6 million PS3s. In fiscal year 2007, Sony expects to once again sell 11 million PS2s while upping its sales of PS3s to 7 million.
A few points here...
First, this is probably the first time that I've not spoken ill of Sony and that's because this story has to do with the PS2. For all of the problems that Sony is currently having with the PS3 (price, supply, lack of games, etc.) they do have the best selling console ever. The PS2 is a great machine with great games. At it's current price of US$129, it's also a great deal and I'd expect that price to go down to US$99 soon.
Second, Sony could learn a few lessons from itself. The reason why the PS2 was so darn successful was because it was all about the games. There were no bells nor whistles. No harddrive. No online play. Just good games.
The PS3, on the other hand, seems to focus on everything but the games. Seriously, name a game for the PS3. "Resistance: Fall of Man" may pop into your head, but what else? Now, ask yourself what the PS3 is known for. The answer will either be the Blu-Ray drive or the very steep price (due to the Blu-Ray drive).
Of course Sony will be adding good games to the PS3 as it matures. It often takes six months to a year for a new console to have a great game. However, they really missed the boat on having one blockbuster game at launch.
What Sony does have going for it, of course, is that it is simultaneously selling the PS2 and the PS3. Although it is hemorrhaging money at this point due to the PS3, the PS2 is a very adequate band-aid.