DOOM3 BFG and Killzone HD.
I downloaded Killzone HD yesterday and had a quick whirl on it to see what it's like. Gotta say it looks great and it's not as fuzzy and washed out as it was. The biggest improvement however is there is no slow down. The original PS2 version had terrible frame rate but for people who are familiar with the first game and still like it, you will notice a huge difference in how it plays. Instantly the game is alot more enjoyable than it ever was and we can play it, how it was supposed to be played.
Comparing it visually to DOOM3 which was released only a few months before Killzone was, its clear how ahead of its time DOOM3 was (I never played it until now so I had no idea). Now that Killzone runs smoothly its clear to see that Killzone's gameplay doesn't feel dated at all (it does if you dont re-map the buttons because the default controls feel weird, but you can literally change any button you want) whereas the visuals (other than guns, character models etc) do look dated. Its the opposite with DOOM3, where the visuals have aged well but the feel of the game and how it plays havent.
Enjoying the hell out of DOOM3 though and Ive heard a few people say it's not scary at all but ive been shitting myself at times.