Edge Reviewed Halo 3, Lair, WarHawk, and PGR4

[GranTurismo]

10 hours on legendary maybe with 4 player co-op with all good players.  Try it on 1 player legendary and see how long it takes.  I still never beat halo 2 on legendary, so that puts Halo2 singe player mode at over 3 years :P