I this the same game as Far Cry on the PC?

No. The Xbox version is a very different version of a similar game. The storyline and the bestial nature of the player's Carver were reimagined for the console release. Far Cry Instincts Evolved, I believe, is somewhat of an updated version of Far Cry Instincts.

From the GameSpot review of Far Cry Instincts:
"LWhen Ubisoft announced last year that it was going to port its hit PC first-person shooter Far Cry to the Xbox, the news generated a lot of skepticism. After all, Far Cry wasn't just one of the best PC shooters of 2004; it was also a technological marvel that pushed PC graphics to the limits. How could it possibly work on the Xbox? Well, it turns out that for starters, developer Ubisoft Montreal threw Far Cry out the window and created a new game from the ground up, one designed to take full advantage of the Xbox's hardware. That's all well and good, but what everyone didn't expect was that Ubisoft Montreal would create a game that's even better than Far Cry, and considering how good Far Cry was, that's saying quite a lot." (www.gamespot.com/xbox/action/farcry/index.html)