Haha, so it would seem.

Well totally ignoring the description of the cover, here's a list of the games I found on a list of 2008 PC games that had a "3" in the title. Obviously, quite a few of them clearly don't remotely fit the description but I'll just put them here anyway.

Gothic 3: Forsaken Gods
Red Alert 3 (obviously not this)
Fallout 3 (obviously not this)
Dracula 3: The Path of the Dragon (seriously doubt it's this)
Magic Ball 3 (Definitely not this, it's a breakout-type game)

And here are ones where the cover fits the description you have at least vaguely:

Devil May Cry 4
Legend: Hand of God
The Chronicles of Narnia: Prince Caspian

uhhh kind of a long shot that doesn't quite fit the criteria, but Last Remnant?
http://www.mobygames.com/game/last-remnant/cover-art/gameCoverId,167971/

I was stumbling through the Internet just now, and the answer hit me out of nowhere.

I couldn't put a title to this game...and then all of a sudden, it all came back to me.

http://www.gamershell.com/static/boxart/large/uk/1772.jpg

The game was Lineage II, not the third of a series, the second :P I'm almost positive this is the game my fuzzy little brain could not remember before...

Anyway, thank you to everyone who provided input! It was helpful =)
This question is now finished!

EDIT: Also, I apologize for getting some of the details wrong...the "third part of a series" bit, the "only waist up visible" bit, and the year...turns out it was more than 4 years ago :P How time flies.

2nd EDIT: Also...I can't mark my own post as a solution, so I am at a loss with what to do with this Question now...