I-8 is the codename for the game that became Resistance: Fall of Man. The project was first shown at E3 2005, but the game shown in that video is almost nothing like the game that we have today.
The only thing in this video that really resembles the final game is 35 seconds into the video you can see a early looking Chimera. The video shows large scale battles fought with hundreds of black op soldiers which is much different then the final games humanity’s losing the war feel. It also appears that you’re fighting other humans along with the Chimera, where in the final game you’re only fighting the Chimera.
In the “Resistance Alpha Video” it’s not known whether or not the game was called Resistance, or I-8 at this point in development you can see that the game now has the look of the final game, but it still has you playing as a black ops soldier, and still has the all out war feel of the first I-8 video. Some noticeable changes are, there are large amounts of enemies onscreen at once, the Chimeras are much more aggressive, and the animations are much better.
The Black Ops soldiers can still be found in the final game, but only as dead bodies that contain hidden messages.
An interesting article about the technical development of the game can be found at Cybergooch.