Alright, I'll bite. What FPS('s) before did you quickly regenerate all your health if you can go a few seconds without getting shot? I'm not trying to be snarky, I'm genuinely curious; I'm a pretty seasoned FPS vet, and as far as I know, Halo was the first game to use this kind of system, which has since become the standard for first-person shooters. There were a few other big things that set Halo apart from the pack. Split-screen co-op is one. While it's not exactly original, I can't think of any good FPS's before Halo that had decent splitscreen co-op. (Perfect Dark tried, but the framerate was pretty terrible.) Seamless vehicle integration was another. While certainly not the first game to incorporate vehicles, few games at the time had vehicles that were as much fun to drive as Halo's warthog, banshee and scorpion tank, and that you could jump into and out of at any time.

Two words: Horse Armor. That said, it is true that "premium" add-ons are much rarer for the PC.

The ease of pirating these add-ons for the PC is probably part of the reason for this. Also, PC gamers have long expected free add-ons and user-created content with there games, whereas this has been all but unheard of for console games until recently.

Not all add-ons are a bad deal, though. As long as these ones aren't too expensive, they look like a pretty good deal. Mirror's Edge may have had a short story mode, but with ranked speed runs and 30-something replayable Time Trial levels, there's really a lot of content for more dedicated players. And these levels look pretty amazing, and really, really open-ended.