Imo the mo-cap, character models, map architecture, gun models etc all look far far better now then it all did on the pre-rendered clip from '05. All that the '05 video has going for it is polished textures and detail, the explosions do look sweet but it's all scripted and pre-rendered.
The '08 level of detail is nearly there, it's still pre-alpha and as it is it's more than I could ask for anyway. People are complaining about it not being 60fps and 1080p, but is that possible? So far the only games I've played with those stats are racing games like Gran Turismo and Wipeout.
This game is top of my highly anticipated games list.