Rockstar’s mega hit Grand Theft Auto IV has been on a long roller coaster over the last 8 months since its release. At least in terms of its Xbox Live Activity Ranking.

When it first released, it was a smash hit that almost immediately dethroned Halo 3 atop the charts, and it stayed there for over a month. Since then, however, it has been up and down.

Remarkably, GTA IV, which is not known for its multiplayer, has held its own against more than a couple juggernauts. In November and December it seemed to find a home at the number five spot, even despite the advances of the highly lauded Left 4 Dead.

Three weeks ago though, that changed, and now GTA IV has been on an uncontrolled slide. This is the second week in a row that the game has fallen down a position. It now rests at number seven, having been most recently bested by Guitar Hero World Tour.

It seems safe from any further declines at this point, however. The three games that lie behind it are Fallout 3, Madden 09, and Fable 2. Unless Madden 09 sees a spike in activity over the Super Bowl weekend, it doesn’t look likely that any of those three will be moving up the charts.

GTA IV faces steep competition in the coming year. We’ll see if it can maintain its ground against the heavy online components of the Lord of the Rings: Conquest, or the widespread popularity of a new game in the Skate series (Skate 2).