IMO, Halo: CE's Heroic, or Legendary's difficulty is way easier than Halo 2. I play better with the idea that I get recharging shield bars. I can beat Halo on Heroic, and Legendary, but even though Legendary will be a pain in the ass, I beat it. I would just throw grenades, and kill everything that I could, than collect more grenades to proceed, which would take quite a long time. Jackals with Beam Rifles in Halo 2 are frustrating as hell to me, and I feel confined in Halo 2 levels. In Halo 1, I could snipe my way out of it most of the time, or kill from a distance, or either taking one out at a time until I recharge. In Halo 2, enemies gang up on me, and escape is hard.
Halo was my main game that I played for a long time, over and over again.