I've always been playing Halo since Halo CE when I was like 2 years old! Now I'm playing through all Halo's on Halo Mcc and Halo 5 on Xbox One 15 years later but my favourite Halos are Halo CE & Halo 3
Halo 3 is my favorite because it is good overall. The multiplayer is great, albeit not quit as good as 2, the campaign is great, albeit the story isn't quite as good as two, the level design is great though and the gameplay is great.
And I'll be honest the game is very nostalgia, I played it when I was 12 and onward, it helped me deal with man emotional problems, and it was the first game I played online.