I'm quite surprised you prefer Halo 2 to be honest - the gross overauto-aim and the unbalanced weapons make it a nightmarish game in my opinion. I do have to agree with the maps though, there aren't enough in Halo 3.
I know Halo 2 isnt perfect its far from it, but Im just being honest here. I'm just not enjoying Halo 3 Multi-player at all so far, also its not the ammount of maps I'm bothered about its the quality of them as well. It just doesnt feel like Halo to me anymore, I've tried to like it, but I cant see myself playing it for the next how many years...
Halo 2:
Lockout
Ascension
Midship
Ivory Tower
Headlong
Coagulation
Burial Mounds
Zanzibar
Waterworks
Colossus
Halo 2 Mappack:
Sanctuary
Turf
Relic
Terminal
Gemini
Elongation
Halo 3:
Epitaph
Snowbound
Highground
Narrows
Valhalla (thats a strong maybe though :/)
Those are the maps that I really enjoy and I kept the mappacks from Halo 2 separate so the list is even bigger for Halo 2 if you combine them.
People joked about Halo 2.5 but quite honestly I would welcome it. An example of what I would be happy with: (this is from a Halo 2 perspective if Halo 3 didnt exist)
-Replace the SMG with the Halo 3 Assault Rilfe as the default starter
-Get rid of the button glitches + Super Jumps
-Nerf the plasma pistol a tad (which is completely useless now in Halo 3, I have yet to disable a moving vehicle with a plasma pistol either)
-Give the current Halo 2 maps a face life and nothing more! (still not liking Last Resort compared to Zanzibar)
-Add some more maps + Gametypes, the new Halo 3 weapons too (just the weapons though and
not the detatchable turrets + equipment)
-Saved Films
-A proper forge and not the gimped version they gave us
I can dream cant I...
The single player I thought they improved immensely and I loved every minute of it and the 4 player Co-op improves it even further, but the multi-player side I cant get to grips with.
NOTE: Its not because I cant play it, since I end up finishing the top of my team almost every game with 25 kills and 10 deaths, its just lost the feeling of what made Halo 2 special to me
