I finished my first Halo Marathon Man today. I played Halo:CE and Halo 2 on PC, then Halo 3 on Xbox 360 all in less than a 24 hour period. I got the 360 controller working on Halo:CE, which allowed me the control (game pad) I have been accustomed to for Halo and Halo 2 on a console, but with the visual appeal I've grown to enjoy from Halo on a PC.
The games haven't aged much to me. Halo:CE is still a great game. Loading screens between levels is a non issue on the PC, so the experience is seamless. I am almost a bit dumb-struck by the fact that I once thought Killzone was a better game (though I still enjoy KZ). Halo 2 on Vista is the same, but with loading screens, which makes little sense to me. Not sure what went wrong, but if the original Xbox good stream the game with less memory, why does my PC version feel unfinished. It's like they went out of their way to add loading screens.
Halo 3 is still to fresh to create a sense of nostalgia, but it rounded out the saga nicely.
If a new game is released that continues the story, that the first three Halo games started, I'd be willing to play through each of them again in my second Halo Marathon Man.