Fixed

Easliy the best game I've played this gen if ever.

MGS4 pretty much had no competition when it released. Not that it is a bad thing. It is good for the developer. They timed it right.

Sometimes being exclusive is a good thing. Games like resistance, uncharted, socom, Left 4 dead, gears might sell less or just same as if they are multiplat. Exclusive will rise hype especially for PS3 and X360 which have 90% same game and both ver not having big gap in sales (compared to PS2 and Xbox + Gamecube)

Userbase isn't everything.

To take a completely different example, the UK government keeps banging on about how they need masses more children studying science, because otherwise apparently we will run out of scientists.

But they miss they point that everybody who is any good at science and likes it will already studying it, and those who aren't good at it will never be good scientists and those who don't like it don't want to be.

So how many kids study science has nearly nothing to do with how many scientists come out the other end.

Same goes for MGS4. The people who wanted it got it, and it makes no difference how many other people have the same console.

there almost If not none piracy one ps3.

when GT4, FF12 , KH2, and MSG3 hit the ps2.
piracy was already on many ps2s, so sales would be lower at least by a million.

there is not such thing on the ps3 so people have to buy their games legally or rent them.

Yeah there arent many exclusive titles on the PS3 like on the PS2. So MGS4 seemes more like a must buy for PS3 owners, whereas you had more options to buy on the PS2

I think that you had answered your own question partially in the title. Loyal fanbase, AAA game, great advertisement campaign, great pedigree, biggest exclusive for a console thus far, not as many exclusives as on previous marketleading platform= great sales ;)

I agree with this. Especially the 1st point. But I think the biggest factor, and something that amazingly seems to get overlooked a hell of alot is that ps2 was LAST GENERATION in which the video game industry although big and growing wasn't as big as it is now. Gaming has been growing at an alarming pace since it's beginnings. Quite simply games just sell more now than they ever did before. This is more evident in game sales particularly than it is in Hardware/console sales. That's why the argument of comparing PS3 sale's to PS2's sales at the same point in their respective lifetimes to justify PS3's poor performance bothers me so much. First of all, they are to different systems with different technological aspects and different manufacturing costs. Even if it sold the exact same as the ps2 and we dont take into account industry growth, the ps3 has to sell at a hire rate to make money. That brings us to the profit margin of the respective consoles which of course is also very different and ps3's magin is much higher. So same numbers don't equal same sales from a money/profit standpoint. But more importantly, 3 million copies of a game sold in 2002 is not the same as 3 million copies sold in 2009. In 2002, 3 million copies was generally an astonoshing number. Nowadays, it's impressive, but not overly so, as even some new IPs this gen have hit that mark, something that was unheard of a decade ago. 

I think MGS3 is undertracked, I found a source that claimed it sold 4.7 million

But when all is said and done I think MGS4 will still sell over 4.7 million

And userbase doesn't always matter that much.

When FFVII was released there was 4.5 million PS owners in Japan, first WEEK (in Japan) FFVII sold 2 million copies...so yeh