To be honest, if it melts my retinas that would be great, but top of my list is for them to solve the perpetual problem of bodies
sliding down hills. Now, I know that no-one has made it around to accurately implementing friction into their physics engine (at least in the case of material friction, to my knowledge) for a commercially released product, but if they could stop that, it would help to make the world more believable - mainly due to the fact that Far Cry was the biggest case of
sliding hillitis i've seen. As far as gameplay is concerned, as long as they include a lot more 'Jungle action' this time around, it'll be just as good as its little brother - although by the sounds of things even that wasn't everyone's cup of tea.