also remember that gta san andreas had a MUCH larger user base to sell on.

Excuse me ?

It sold 52k units last week..

28k on PS3, 24k on 360..

it hasnt been a failure but it has been dissapointing .. san andreas was twice as big as gta4 and it had more features

success, great sales, great reviews

1. I'm mentioning Xbox sales because it seems more fair to compare the two consoles which GTA:SA launched on to the two consoles GTA IV launched on. PC data is notoriously hard to get and unreliable, so I left it out.

2. A smaller userbase is probably one of the biggest reasons why the series has peaked. Very astute of you. Since the release of GTA IV, it's console userbase has grown by about 7.5 million units. In a similar timeframe, GTA:SA's userbase grew by about 12.5 million units. And the massive userbase expansion of releasing the game on Xbox is yet to come in that timeframe.

3. I think the publisher cares that the budget was bigger. Or maybe not. Take 2 doesn't quite seem to know how to make money. Though Ail does make a good point that reliable returns are reliable returns. Can't expect to strike gold in every mineshaft.

4. As somebody with a green nametag, you should be above putting words in other people's mouths. I never used the word 'flop.' I used the word 'peaked.' Do I have to expain to you how these words mean different things?

Legs for GTA IV have not been looking very favourable compared to GTA: SA. In many recent weeks, the PS2 version of GTA: SA has outsold the PS3 version of GTA IV in Americas. I wish the game comparison tool was flexible enough for me to get a good impression of how often this was happening, but I did notice it several weeks in a row. Throw in the more sluggish growth of GTA IV's userbase mentioned above, and I doubt it will manage to outpace GTA: SA in the long run.

When I see the figures I see a success

In the end you can't expect every well known gaming franchise to keep selling more with every new iteration.
As the industry matures the competition is becoming fiercer and it is hard to keep repeating past success.
The fact that every 5 years or so a new generation starts and the user base isn't the same in size for every new release makes comparison difficult too.

However GTA4 has demonstrated that the franchise is still very powerfull, in very good health and very profitable...
As for development costs I persist, I believe GTA is the kind of franchise where the developer has to invest more every sequel as it is what the customer expects. When you play GTA4 you want to be wowed and those tiny little details that keeps achieving that effect ( like those shows you can watch on the TV in game) is what in the end differentiates GTA4 from any possible competitor...

It is my favorite game on Xbox 360 and PS3 so it is a massive success to me.

It's also a success in terms of being better then the Snoozefest which is SA.

What? How was SA a snooze fest?