Halo 2 > Halo 3 > Halo 3 ODST > Halo Reach > Halo CE
Based on campaigns.
Posted by: beastage1458
I have only played through the entire game once (legendary), and I found it to be pretty enjoyable. Of course, it didn't compare to the previous Halo's, but it was fun because it was new. I doubt it would be any fun at all if I were to play it again, whereas Halo 2 would still be awesome (as long as it's not on legendary).
Whenever all my friends are offline I usually play a mission or two of Halo 2. Never gets old.