Halo 3 was the last true Halo. It's multiplayer pushed the gameplay limits as far as it could without completely ruining the integrity of the game. Reach/ODST/Halo 4 are what 15 years olds think Halo is (because they weren't around for the original trilogy), so naturally all the new gamebreaking perks/upgrades/weapons/garbage maps seem amazing to them. It's also edgy for them to trash CoD because it's popular and has multiplayer that is actually fun and works.
Im 24 years old, been a huge Halo fan since CE. I enjoyed ODST, Reach(campaign, not multiplayer), and I'm loving Halo 4. Not everybody that disagrees with you is 15 years old. Stop being a jackass, and be a little more original instead of calling everybody 15 year olds. That's so old.