But it was the same game

Not necessarily. Halo 2 on the PC suffered from networking issues at times and tanked some lower end machines, for a 3 year wait, it should not have had these issues. in short, it gown down marked for the same reason Duke nukem forever did.

Yes but not warrant that much of a difference in score surly?
I thought Duke Nukem Forever was fine technically it was just everything else like trying to be funny and the game play, so that's not a fair comparison in that sense, do you mean in that time had not been so kind to Halo 2 and the Duke?

maybe not to much time, more so that the halo 2 pc release came out the same year as halo 3. Lots of comparisons were probably made, unfavorably for halo 2