I think I would like to know what some of your opinions are about your favorite halo game
Just to let you know my favorite halo game is halo 3
Halo 2 is my favorite
Reach/H2. Still can’t decide on either.
reach all the way
Reach and Halo 2.
If you’re referring to campaign play then Halo 2 I enjoyed the most but I still haven’t played Reach or Halo 4. For multiplayer gameplay then Halo 3 definitely.
Halo 1 or Halo 2 for me! Halo 1 was so revolutionary and had a beautiful simplicity that is missing from every other Halo title. Halo 2 had, arguably, the best multiplayer out of all the games, plus had a great double story with Chief and the Dervish… uh, I mean Arbiter! :o lol
Either Halo 2 or post T.U. Reach.
Halo Reach. It’s funny, because when I bought the game I hated everything about it, but now it’s my favourite Halo game.
I’m going to have to stand up for ODST here. ODST’s campaign was the first Halo game that actually made sense to me. The way the campaign tied together and progressed from mission to mission. Personally, I never knew why I was somewhere in H1-3, just that I had to kill tons of fools! Anyway, the ODST campaign was amazing, and ODST firefight was the most fun I’ve ever had in a Halo game. Tack on that the fact that the voice actors are from Firefly and Battlestar Galactica, and you’ve got me sold.
Reach.
I just love the level design, and the way it flows cleanly and naturally between areas. Also, when playing on legendary, the difficulty feels reasonable, although it is much harder than some of the earlier Halos. It’s just that kind of frustration where you know it’s YOUR fault that you’re failing. Not the developers’ faults. In earlier games, the level design felt kind of bullsh*t.(i.e. Truth and Reconciliation in Halo: Combat Evolved)
Halo 3, too many fun memories. So much wasted time…
Halo 2, Loved finding each skull and being able to use it to crush all of the grunts.
Halo 2, Halo 3 ODST, Halo 3, Halo 4(Campaign/Spartan Ops only)
Halo Reach!
Halo 2 and Halo 4.
Reach and 3 
Campaign? Uhm. Can’t choose because I enjoy the crap out of all their campaigns.
Multiplayer?
In order:
Halo 2 (competitive)
Halo 3 (Competitive and made me feel like I earned it)
Halo 4 (Fun, not competitive and no real achievement to continuous winning)
Halo Reach (Fun, only competitive in certain areas, but overall entirely too different than Halo 3 and thus different than my likings.
Halo CE. This didn’t have MP for Xbox unless you routed some stuff through a computer and a program, so there was never a way to try it without split-screen or LAN parties. This game was INSANELY fun and easily the ground layer for my Halo addiction, but revisiting this online only proves to me how some old memories should never be revisited, as I now barely enjoy the multi-player aspect due to poor spawns and over-powered pistol.
Halo 1, Halo 2, Halo 3… Nothing is better… end of story